Javier Márquez — Senior Backend Developer

developer.json
{

                                    "name": "Javier Márquez",
                                
                                    "role": "Senior Backend Developer",
                                
                                    "status":
                                    "Available for senior backend developer roles — Remote or hybrid (Mexico City)",
                                
                                    "focus":
                                    ["APIs", "Systems",
                                    "Performance"]
                                
}

Senior backend developer with 10+ years of experience building robust enterprise systems, high-performance APIs and complex financial integrations. Specialized in PHP/Laravel, async processing, CFDI electronic invoicing, payment processor integrations and business process automation through event-driven architectures.

Explore my work Start a conversation

$ cat ~/.profile

                                        →
                                        10+ years of backend development experience with PHP/Laravel and C#/.NET
                                    
                                        →
                                        Backend of 4 microservices in production with 120+ models and async orchestration
                                    
                                        →
                                        End-to-end automated CFDI 4.0 invoicing reducing >80% manual intervention
                                    
                                        →
                                        Integration with 3 payment processors with proprietary formats and automatic reconciliation
                                    
                                        →
                                        Nationwide backend systems — 30,000+ users, 35 offices

01.

About Me

Senior backend developer with 10+ years of experience building robust enterprise systems, high-performance APIs, and complex financial integrations. Career spanning government, healthcare, NGOs, and cybersecurity — from microservice ecosystems with 120+ models and end-to-end invoicing to REST APIs used by multiple clients (web, mobile, and public portals). Hands-on experience with C#/.NET in nationwide mission-critical systems. Proven ability to design scalable backends, automate critical flows with queues and jobs, and integrate external services while meeting fiscal and financial standards.

My Approach

Code as product

I write clean, tested code prepared to evolve. Every module must be maintainable by someone else without needing explanation.

Automation over manual intervention

If a process repeats, it gets automated. Jobs, observers, domain events and async pipelines eliminate human errors and free up operational time.

Pragmatic simplicity

Complexity must be justified with measurable value. I prioritize direct solutions — the right abstraction solves today's problem without blocking tomorrow's.

End-to-end responsibility

I get involved from database design to production deployment. An endpoint isn't done until it works under real load.

// Ideal Opportunities

Roles where I can build solid and scalable backends — designing APIs, implementing complex integrations, optimizing performance with async processing and solving business domain problems with clean, well-tested code.

02.

Experience

REST APIs and integration contracts

Design and implementation of authenticated REST APIs (Sanctum, JWT) with versioning, rate limiting and specialized middleware. Integration with SOAP/WSDL protocols for fiscal compliance, batch file generation for payment processors, and real-time communication (Pusher, SignalR) with segmented channels.

Electronic invoicing and financial integrations

Complete CFDI 4.0 invoicing cycle: stamping via PAC (SOAP/WSDL), payment supplements, cancellation with regulatory reasons, partial and global invoicing. Direct debit with 3 payment processors (HSBC, AMEX, PROSA) via batch files with proprietary formats and automatic bank response reconciliation.

Async processing and queues

Critical flow orchestration with Bus::chain and chained jobs (stamping → PDF → email). Background processing with Redis/queues to decouple intensive operations from UI. Recurring expenses with events/listeners that automatically generate future movements.

Data modeling and advanced Eloquent

Schema design with 100+ tables, Single Table Inheritance, polymorphic relationships, Global Scopes for segmentation, application-level multi-tenancy, UUIDs as primary keys, cascade soft deletes and full-text search with MeiliSearch/Scout.

Event-Driven Architecture and automation

13+ observers for business cascade automation (automatic invoicing, financial synchronization, email sending). Domain events with specialized listeners for package generation, correspondence and accounting processes.

Security, authorization and multi-tenancy

Centralized RBAC with seeder-versioned permissions (29 releases), ~100 authorization policies, custom middleware (ForceJsonResponse, configurable rate limiting), SAT digital certificate validation and multi-tenancy with automatic session context filtering.

AI-assisted development and AI API integration

Active AI integration in backend development workflow: GitHub Copilot and Cursor for code generation and refactoring, ChatGPT and Claude for debugging, complex query design and technical documentation. OpenAI API integration in projects: embeddings for semantic search, RAG (Retrieval Augmented Generation), structured prompt engineering and AI endpoint development with dynamic content generation.

Key Achievements

                            -rw-r--r--
                            End-to-end CFDI 4.0 invoicing pipeline with async orchestration (stamping → PDF → email)
                        
                            -rw-r--r--
                            Sanctum-authenticated REST API for sponsor portal with registration, payments and invoice downloads
                        
                            -rw-r--r--
                            Direct debit system with 3 payment processors and automatic reconciliation
                        
                            -rw-r--r--
                            4-microservice ecosystem with independent databases, centralized RBAC and shared-core
                        
                            -rw-r--r--
                            Seeder-versioned permission system with incremental releases (29 releases without destructive migrations)
                        
                            -rw-r--r--
                            Open source Composer package with 15,017+ installs and organic adoption

03.

Featured Projects

project_1.md

Esfera Médica — Microservice Backend Evolution

Esfera Médica | Senior Backend Developer | 2023-01-01 – Present

Health / Commerce freelancer

Maintenance and continuous evolution of the backend of a 4-microservice ecosystem that I designed and implemented previously as an employee. New integrations, business modules and optimization of existing flows.

$ Stack: PHP 8+, Laravel 9, Laravel Nova, Livewire 2, MySQL (multi-database), MeiliSearch, Pusher, Redis, Amazon S3, Docker

## Business Context

A 4-microservice ecosystem in production (Core, Billing, Administration, Medical Records) with independent databases, centralized RBAC, and async orchestration. I returned as a freelancer to continue evolving the backend.

## Challenge

Need to incorporate new business modules (commissions, advanced clinical records) into the existing ecosystem without breaking contracts between microservices or affecting production stability.

## Objectives

✓ Incorporate new modules without breaking contracts between microservices
✓ Keep async orchestration and queue processing stable
✓ Continue reducing technical debt in the backend

## Technical Approach

Backend development of new modules respecting existing bounded contexts between microservices. Implementation of commission management module with financial calculation logic aligned to the Billing model. Backend for medical record printed formats: optimized queries, data transformation and PDF generation with DomPDF. Maintenance of async invoicing jobs and synchronization between microservices.

## Architecture Decisions

Modules as bounded context extensions

New modules integrate as extensions of existing services (commissions in Billing, records in Medical Records) instead of creating additional microservices, maintaining cohesion and avoiding unnecessary coordination complexity.

## Impact & Results

→ Serving ~950 patients, supporting complete ecosystem backend operation

→ Recurring generation of 500–600 monthly invoices processed asynchronously

→ Up to 70% reduction in administrative work time through backend digitization

→ Ecosystem operational continuity without interruptions or performance degradation

## Key Insights

Resuming a backend you designed allows evaluating modeling decisions with temporal perspective. Financial modules require strict decimal precision and complete calculation auditing.

project_2.md

Evently — Digital Invitation Platform Backend

Evently | Backend Developer | 2025-01-01 – 2025-03-01

Events / SaaS personal

Complete backend design and implementation of a SaaS platform for digital invitations. Concept to production in ~6 weeks: domain modeling, API, service layer, testing and CI/CD.

$ Stack: PHP 8.4, Laravel 12, Filament 4, Inertia.js, TypeScript, MySQL 8, Docker, PHPUnit 11

## Business Context

Personal project where I implemented the complete backend from scratch: data modeling, business logic, security, visitor tracking and gallery system with moderation.

## Challenge

Design a backend supporting multiple invitation types (personalized and generic) with common behaviors but differentiated flows, visitor tracking with privacy, and collaborative gallery with configurable limits.

## Objectives

✓ Implement backend extensible to new invitation types without modifying existing code
✓ Guarantee visitor privacy (IP hashing, cookie UUIDs)
✓ Deliver complete backend with testing in 6 weeks

## Technical Approach

8 Eloquent models with complex relationships and 17 migrations. Domain interfaces (Visitable, HasGuest) for polymorphism between invitation types. Service layer (PhotoService) decoupling business logic from controllers. UUID-based routing to prevent enumeration attacks. Visitor tracking with SHA-256 IP hash for privacy and bot detection (CrawlerDetect). Dedicated Form Requests for RSVP confirmation/declination validation. Reusable trait HandlesInvitationDisplay encapsulating cross-cutting concerns. Externalized configuration via environment variables for gallery parameters. Automatic crawler detection for serving OpenGraph meta tags. Admin panel with Filament 4: 9 CRUD resources. Complete audit with Spatie Activity Log on all main models.

## Architecture Decisions

Domain interfaces over inheritance

Visitable and HasGuest allow adding new invitation types without modifying existing code (Open/Closed Principle).

UUIDs in public routes

Prevents enumeration attacks decoupling URLs from internal IDs.

Service layer for business logic

PhotoService centralizes visitor identity resolution, gallery validations and storage operations, keeping them out of controllers.

## Impact & Results

→ Complete backend in production in ~6 weeks

→ 8 models, 17 migrations, 9 Filament resources

→ 13+ tests (7 unit + 6 integration/feature)

→ MVP iterated in production for one month with CI/CD

## Key Insights

Domain interfaces scale better than inheritance for modeling behavior variants. Externalizing configuration to environment variables allows adjusting logic in production without redeployment.

project_3.md

Default Value Filterable — Open Source Package

Open Source | Author and Maintainer | 2024-01-01 – Present

Open Source / Laravel Nova Ecosystem open-source

Open-source Composer package extending Laravel Nova through a custom macro. Demonstrates ability to design public APIs with low adoption friction and maintainable code across versions.

$ Stack: PHP 8.1+, Laravel Nova 5.0

## Business Context

Recurring pain point in the Laravel Nova ecosystem: the impossibility of setting default values on filterable fields with customizable logic.

## Challenge

Laravel Nova lacked a native way to set default values on filterable fields with customizable filtering logic.

## Objectives

✓ Design public API with zero adoption friction
✓ Maintain cross-version compatibility between Nova major versions

## Technical Approach

defaultFilterable macro integrating transparently with existing Nova fields (no type replacement required). Support for customizable filtering callbacks. Semantic versioning: v1.0.0 (Nova 4) → v2.0.0 (Nova 5). Complete technical documentation oriented toward adoption.

## Architecture Decisions

Macro over custom field

A macro-based approach reduces adoption friction to zero: developers don't need to replace their existing field types. It integrates as a transparent decorator.

## Impact & Results

→ 15,017+ installs via Packagist

→ 5.0/5 rating on NovaPackages

→ 0 open issues: stable API with no reported incidents

→ 2 releases maintaining compatibility between Nova major versions

## Key Insights

Public API design requires minimizing breaking changes and maximizing backward compatibility. Organic adoption validates solving a real problem.

Packagist GitHub Nova Packages

project_4.md

Fundación Lazos — Cloud-Based CRM Backend

Fundación Lazos | Senior Backend Developer | 2023-01-01 – 2025-01-01

NGO / Fundraising freelancer

Designed and developed from scratch the complete backend of a cloud-based CRM that replaced a legacy system. ~115 tables, ~120 Eloquent models, REST API, CFDI invoicing, direct debit with 3 payment processors and event-driven architecture.

$ Stack: PHP 8.1+, Laravel 10, Laravel Nova 4.32, MySQL 8.0, Laravel Sanctum, Spatie Laravel Permission, Docker, NGINX

## Business Context

Legacy CRM (SugarCRM) with unsalvageable technical debt. Need for a completely new backend supporting sponsorships, donations, electronic invoicing, direct debit, schools, correspondence and a REST portal for sponsors.

## Challenge

Build a backend integrating 10+ interconnected business modules, 3 payment processors with proprietary formats, CFDI electronic invoicing via SOAP, and a REST API for external consumption (mobile and web) — all with per-resource granular authorization and process automation.

## Objectives

✓ Build cloud-based backend to replace legacy CRM
✓ Implement financial integrations with 3 payment processors
✓ Automate complete CFDI invoicing cycle
✓ Design REST API consumable by multiple clients (mobile, web)

## Technical Approach

Data model: ~115 tables, ~120 Eloquent models with STI for prospects, donations, conversations and users differentiated via Global Scopes. Polymorphic relationships for benefactors, donations and fiscal data. Direct debit: batch file generation in proprietary formats for HSBC (Domi482), AMEX (Domi700) and PROSA (Domi91). Bank response processing with automatic reconciliation. Flow: Nova Action → DueDateService → flat file → bank processing → reconciliation. Complete CFDI invoicing: SOAP/WSDL integration with Finkok PAC — on-demand stamping, payment supplements, cancellation with regulatory reasons, global invoices. Async flow: Donation → Observer → CollectionsService → Job (CreateCfdi) → SOAP → XML/PDF storage. SAT digital certificate validation (.cer/.key) via CertificateService. PPD invoice, payment supplement and income invoice automation. REST API (Sanctum): sponsor portal — registration, profile, gateway payments, sponsorship queries and invoice downloads. Event-Driven Architecture: 13 observers for business cascades (automatic invoicing, cascade soft deletes, email sending). Domain events (SponsorshipCreated, SchoolDroppedOut) triggering specialized listeners. Granular authorization: ~100 policies, 34 Nova Actions. 8 custom validation rules (RFC, CURP, CLABE). Custom middleware: ForceJsonResponse (API), EnsureProfileIsCreated, ConditionalThrottle. Backend for foundation web portal. Complete i18n. Infrastructure recovery after critical power failure.

## Architecture Decisions

On-demand stamping over prepaid packages

Cost analysis showed that per-transaction invoicing delivered roughly 3x better cost efficiency than fixed packages.

STI for entity hierarchies

Prospects (3 types), donations (2 types) and users modeled in single tables with Global Scopes — simplifies cross-cutting queries without multiplying tables or migrations.

Observers for automation

Creating a sponsorship automatically triggers image generation, packages and letters. Observers centralize side effects avoiding duplicated logic in controllers.

Batch files over payment APIs

All 3 processors require integration via flat files with proprietary specifications — they don't offer REST APIs. Automatic response reconciliation eliminates manual reconciliation.

## Impact & Results

→ Backend with ~115 tables, ~120 models, 34 Nova Actions, ~100 policies and 13 observers

→ Roughly 3x improvement in invoicing cost efficiency

→ Management of ~9,453 sponsors/donors and ~8,075 monthly transactions

→ Complete infrastructure recovery after critical power failure

→ Successful legacy CRM replacement eliminating accumulated technical debt

## Key Insights

Financial integrations with proprietary formats require byte-by-byte validation and processor-specific edge case handling. CFDI stamping via SOAP demands robust error handling, timeouts and retries.

project_5.md

DR México — Mission-Critical Backend Stabilization

DR México | Backend Software Engineer | 2023-01-01 – 2024-01-01

Security / Government freelancer

Takeover of the backend of multiple mission-critical systems for government entities after massive team resignation. Stabilization, diagnosis and maintenance of 10+ projects with heterogeneous stacks.

$ Stack: .NET 6, ASP.NET Core, C#, SQL Server, SignalR, REST API, Python, PHP with Symfony, Angular

## Business Context

The entire technology team had resigned. Critical systems at risk of contractual penalties. Backend ecosystems with multiple technologies (.NET, Python, PHP/Symfony) without documentation or maintainer.

## Challenge

Take control of critical backends without documentation, diagnose and fix bugs in 10+ projects with different technologies, and guarantee SLA compliance with government entities.

## Objectives

✓ Stabilize critical backends without documentation in minimum time
✓ Guarantee 100% SLA compliance in government contracts
✓ Maintain real-time communication between distributed components

## Technical Approach

Audit and diagnosis of 10+ legacy backends with heterogeneous technologies. Stabilization of REST APIs (ASP.NET Core) feeding the multi-channel ecosystem (web, desktop, kiosks, displays). Maintenance of SignalR layer for real-time communication between distributed components (advisor widgets, queue displays, kiosks). SQL Server database administration and server management (Linux for apps, Windows Server for DB). Critical ticket resolution with strict SLA severity scheme. Backend for queue and appointment system in 35 offices nationwide with 50+ simultaneous windows.

## Architecture Decisions

Prioritization by operational impact

Strict SLA severity scheme with immediate resolution for incidents affecting public service. Diagnoses prioritized by contractual risk, not technical complexity.

## Impact & Results

→ ~5 heterogeneous systems stabilized simultaneously

→ 100% SLA compliance: total elimination of contractual penalties

→ Deployed in 35 offices nationwide with 50+ simultaneous windows

→ Wait time reduction from 90 minutes to 25 minutes

## Key Insights

Reverse engineering of undocumented backends requires request tracing, DB schema analysis and disciplined code reading. Legacy system stabilization demands surgical changes with maximum impact coverage.

project_6.md

Tekman Education — Educational Platform Backend Core

Tekman Education | Senior Backend Developer | 2023-01-01 – 2023-06-01

Education / EdTech salaried

Backend development in the CORE of educational platforms under hexagonal architecture and Domain-Driven Design in a Scrum environment with international team.

$ Stack: PHP, Symfony 4, Hexagonal Architecture, DDD, SOLID

## Business Context

Spanish EdTech company with educational platforms for Europe and Latin America. Mature codebase under strict hexagonal architecture with DDD patterns.

## Challenge

Complex educational domain (multiple countries, curricula and regulations) requiring strict adherence to bounded contexts and domain patterns to maintain testability and scalability.

## Objectives

✓ Contribute to backend CORE respecting hexagonal architecture and DDD
✓ Identify and resolve performance bottlenecks
✓ Maintain code quality under SOLID standards

## Technical Approach

Business logic development in the application CORE respecting established bounded contexts. Data, process and code analysis to identify backend bottlenecks. Query optimization and business flows maintaining hexagonal layer separation. Collaboration with international team under Scrum.

## Architecture Decisions

Consistency over innovation

In a mature codebase with established hexagonal architecture, respecting existing patterns reduces architectural drift risk and facilitates peer review.

## Impact & Results

→ Improved maintainability and scalability under hexagonal architecture and DDD

→ Optimization of response times in critical queries

→ Reduction of production incidents through SOLID best practices

## Key Insights

Hexagonal architecture enforces domain boundaries that make every layer independently testable. The discipline of adhering to established patterns generates more value than introducing new approaches in mature codebases.

project_7.md

Esfera Médica — 4-Microservice Backend Architecture

Esfera Médica | Senior Backend Developer / Architect | 2020-01-01 – 2023-01-01

Health / Commerce salaried

Design and implementation of the complete backend of a 4-microservice ecosystem for a medical business group. 56 models in Billing alone, async CFDI invoicing orchestration, centralized RBAC with 29 permission releases and 34 custom Nova components.

$ Stack: PHP 8+, Laravel 9, Laravel Nova, MySQL (multi-database), MeiliSearch, Pusher, Redis, Amazon S3, DomPDF, Maatwebsite Excel, Docker

## Business Context

Medical business group with no digital system (greenfield). Needed a complete backend to manage clinical operations, electronic invoicing, financial administration and medical records across multiple clinics.

## Challenge

Build the backend of 4 interconnected business domains with independent databases, multi-tenancy across clinics, CFDI 4.0 invoicing with async orchestration, segmented broadcasting per medical team and a permission model that evolves without destructive migrations.

## Objectives

✓ Implement backend of 4 microservices with independent databases
✓ Automate complete CFDI 4.0 invoicing cycle
✓ Design evolutionary permission model without destructive migrations
✓ Implement broadcasting segmented by business context

## Technical Approach

Core (Identity and RBAC): Centralized permission model with Spatie Permission consumed by all 4 microservices. 29 permission releases via incremental seeders. Normalization observers (CompanyObserver, BusinessCenterObserver). Dedicated Docker network as the communication backbone. Billing (56 models, 50 migrations): End-to-end CFDI 4.0 cycle — XML generation, PAC stamping, SAT queries, regulatory cancellation, and acknowledgments. Async orchestration with Bus::chain: CreateCfdiJob → CfdiXmlToPdfJob → SendCfdiEmailJob. Cloud storage (S3) for fiscal evidence. POS with daily and partial closings. Livewire self-invoicing portal for patients. Administration (43 migrations, 17 Nova Actions): Financial management for accounts, movements, income, expenses, loans, and budgets. Accounting automation via events — creating a movement triggers jobs for derived operations. Recurring expenses with listeners that generate future movements automatically. Fiscal compliance: SAT cataloging and RFC validation. Medical Records (27 models, 43+ migrations): Real-time broadcasting with Pusher — channels segmented by medical team and business center for office ↔ pharmacy synchronization. Full-text search with MeiliSearch/Scout. 15+ PDF medical templates. Clinical management: ICD-10, vital signs, therapeutic plans, and medications with JSON dosages. Multi-tenancy: Companies → MedicalTeams → BusinessCenters with automatic session-context filtering via shared-core. 34 custom Nova components packaged as independent Composer packages. Development team leadership, code review, and 25+ continuous releases. Administration of 4 databases, cloud servers, and repositories.

## Architecture Decisions

Seeder-versioned permissions

29 incremental releases enable controlled RBAC evolution without destructive migrations, maintaining complete security change traceability.

Async orchestration with Bus::chain

Decouples fiscal flow from UI. If stamping fails, doesn't block the user. If email fails, doesn't affect PDF. Each step independently restartable.

Context-segmented broadcasting

appointments.medical_team.{id}.business_center.{id} guarantees each office only receives relevant events, reducing WebSocket traffic and improving security.

Shared-core as Composer package

Multi-tenancy, helpers and shared configuration between microservices without code duplication, maintaining independent versioning.

## Impact & Results

→ 4-microservice backend ecosystem in production with continuous operation

→ CFDI 4.0 invoicing automation reducing manual intervention by more than 80%

→ >70% reduction in critical process times through async processing

→ Real-time synchronization (<1s) between offices and pharmacy

→ Full-text search reducing query times from seconds to milliseconds

→ 25+ production releases maintaining system stability

→ 34 custom Nova components standardizing backoffice operations

→ 100% fiscal documents centralized in cloud storage

## Key Insights

Async processing with chained jobs is essential for flows integrating external services with variable latencies. Seeder-versioned permissions elegantly solve RBAC evolution in production without downtime.

project_8.md

DR México — Nationwide Backend Systems

DR México | Backend Software Engineer | 2018-01-01 – 2020-01-01

Security / Government / Technology salaried

Backend development of nationwide mission-critical systems for government institutions. Hardware integration (biometrics, RFID), image processing and APIs for multi-site platforms.

$ Stack: .NET, C#, C++, SQL Server, Python, PHP with Symfony

## Business Context

Security technology company needing robust backends for systems deployed in hundreds of stations nationwide.

## Challenge

Build backends integrating multiple hardware devices (biometrics, RFID, cameras, printers) with centralized databases, and APIs for multi-site platforms with automated configuration.

## Objectives

✓ Implement backends with hardware integration at national scale
✓ Design APIs supporting multiple frontends per audience
✓ Guarantee efficient biometric data processing

## Technical Approach

Biometric Enrollment System (Project Leader): Backend for identity registration with 7+ hardware device integration. Image processing with OpenCV (facial detection, photo normalization). Active Directory SSO connection. SQL Server persistence. Deployed in hundreds of buildings. Appointment Management Platform (Project Leader): Backend API with dual frontend — Vue.js for public portal and Blazor Server for administration. Institutional database integration. Appointment scheduling system with location/procedure availability. Embedded device programming in C++ with socket communication. Windows services for backup automation and file change detection. JWT authentication and API ↔ frontend communication (Angular–PHP).

## Architecture Decisions

Plug-and-play device integration

Installer that automatically registers and configures 7+ peripheral drivers, eliminating manual configurations in hundreds of stations.

OpenCV for processing pipeline

Automated normalization with facial detection guaranteeing homogeneous records reusable across modules.

Audience-differentiated APIs

Endpoints optimized for public portal (lightweight, cacheable payload) vs admin panel (rich, paginated data).

## Impact & Results

→ 100% contractual compliance across all deliveries

→ More than 30,000 employees enrolled with uninterrupted access

→ System operating in hundreds of buildings nationwide

→ Sustained stability without critical incidents throughout the entire period

## Key Insights

Backends integrating hardware require robust driver abstraction and per-device timeout handling. Windows services with file system watchers are the cleanest solution for process automation in corporate environments.

project_9.md

Warriors LABS — Distributed Security Backend

Warriors LABS | Backend Developer / Project Leader | 2016-01-01 – 2018-01-01

Cybersecurity / Software Development salaried

Development of the backend layer and distributed services of a white-label corporate security solution. Leadership of 6-developer team.

$ Stack: .NET Framework 4.7, C#, C, C++, WCF

## Business Context

Cybersecurity company developing a corporate antivirus distributable as white-label for their client base.

## Challenge

Implement the backend of a threat detection system with hybrid scanning pipeline (signatures + heuristics), integration with native C++ high-performance engine, and secure communication between distributed services.

## Objectives

✓ Implement hybrid real-time detection pipeline
✓ Design secure communication between distributed services
✓ Deliver white-label product ready for commercial distribution

## Technical Approach

Scanning pipeline backend: signature comparison + heuristic analysis. C# ↔ C++ interoperability for native detection engine integration via C++/CLI wrapper. Windows services (WCF) for scanning, updates, coordination and real-time protection. File system watchers and active process monitoring for real-time detection. Decoupled update system for releases without reinstallation. Secure inter-service communication (WCF netTcpBinding). Leadership of 6-developer team + parallel 4-person Helpdesk team.

## Architecture Decisions

C++/CLI wrapper for native engine

Exposition of managed interfaces consumable from C# with direct access to high-performance libraries and memory control for low-level analysis.

## Impact & Results

→ Coordination of teams of 6 and 4 developers in parallel projects

→ White-label security product delivered ready for commercial distribution

→ Hybrid detection pipeline operating in real-time

→ Decoupled architecture facilitating updates without full reinstallation

## Key Insights

Windows services with WCF offer microservice-like decoupling in corporate on-premise environments. The C++/CLI native wrapper is the cleanest solution for integrating high-performance libraries in .NET ecosystems.

project_10.md

Telecomm — Institutional IT Inventory Backend

Telecomm | Intern Developer | 2016-01-01 – 2016-06-01

Telecommunications / Government intern

Development and maintenance of the institutional IT inventory system backend.

$ Stack: PHP, MySQL, HTML, CSS, JavaScript, jQuery

## Business Context

Government telecommunications institution requiring backend maintenance and evolution of their IT inventory system.

## Challenge

IT inventory backend requiring new modules, database optimization, security vulnerability fixes and server migration.

## Objectives

✓ Develop new backend modules for institutional IT inventory
✓ Fix security vulnerabilities and optimize database

## Technical Approach

Design and programming of new backend modules for the IT inventory. MySQL database maintenance, debugging and optimization. Security vulnerability fixes and backend input validation. Web platform migration to higher-performance server.

## Architecture Decisions

Server migration for improved performance

Migration to higher-performance server improving availability and overall system performance.

## Impact & Results

→ Improved data integrity reducing inconsistencies

→ Identification and correction of security vulnerabilities

→ Successful migration improving availability and overall performance

## Key Insights

Database maintenance and optimization are critical for data integrity. Security vulnerability identification requires systematic code review.

04.

Technical Expertise

                            Languages
                        
                                PHP
                                
                                                                        Advanced
                                                                                                            10y
                                                                    
                                C# / .NET
                                
                                                                        Intermediate–Advanced
                                                                                                            5y
                                                                    
                                JavaScript / TypeScript
                                
                                                                        Intermediate–Advanced
                                                                                                            10y
                                                                    
                                C / C++
                                
                                                                        Intermediate
                                                                                                            3y

                            Backend frameworks
                        
                                Laravel (6–12)
                                
                                                                        Advanced
                                                                                                            8y
                                                                    
                                Laravel Nova
                                
                                                                        Advanced
                                                                                                            5y
                                                                    
                                Laravel Sanctum
                                
                                                                        Intermediate–Advanced
                                                                                                            4y
                                                                    
                                Symfony (2–5)
                                
                                                                        Intermediate–Advanced
                                                                                                            4y
                                                                    
                                ASP.NET Core
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                .NET Framework 4.7/4.8
                                
                                                                        Intermediate–Advanced
                                                                                                            4y
                                                                    
                                API Platform
                                
                                                                        Intermediate
                                                                                                            2y

                            Processing and queues
                        
                                Laravel Queues / Jobs
                                
                                                                        Advanced
                                                                                                            6y
                                                                    
                                Redis
                                
                                                                        Intermediate–Advanced
                                                                                                            4y
                                                                    
                                Bus::chain (orchestration)
                                
                                                                        Advanced
                                                                                                            4y
                                                                    
                                Event-Driven (Observers/Listeners)
                                
                                                                        Advanced
                                                                                                            5y

                            Databases
                        
                                MySQL
                                
                                                                        Advanced
                                                                                                            10y
                                                                    
                                SQL Server
                                
                                                                        Intermediate
                                                                                                            5y
                                                                    
                                PostgreSQL
                                
                                                                        Intermediate
                                                                                                            2y
                                                                    
                                MeiliSearch
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                Redis
                                
                                                                        Intermediate–Advanced
                                                                                                            4y

                            Integrations
                        
                                CFDI 4.0 / SOAP / WSDL (Finkok PAC)
                                
                                                                        Advanced
                                                                                                            4y
                                                                    
                                Payment processors (HSBC, AMEX, PROSA)
                                
                                                                        Advanced
                                                                                                            3y
                                                                    
                                Pusher / WebSockets
                                
                                                                        Intermediate–Advanced
                                                                                                            4y
                                                                    
                                SignalR (.NET)
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                Amazon S3
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                OpenAI API
                                
                                                                        Intermediate
                                                                                                            2y
                                                                    
                                Active Directory / SSO
                                
                                                                        Intermediate
                                                                                                            3y

                            DevOps and infrastructure
                        
                                Docker
                                
                                                                        Advanced
                                                                                                            5y
                                                                    
                                NGINX
                                
                                                                        Intermediate
                                                                                                            5y
                                                                    
                                Git / GitHub / Bitbucket
                                
                                                                        Advanced
                                                                                                            10y
                                                                    
                                CI/CD (Bitbucket Pipelines, Laravel Forge)
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                Laravel Forge
                                
                                                                        Intermediate
                                                                                                            3y

                            Testing
                        
                                PHPUnit
                                
                                                                        Advanced
                                                                                                            6y
                                                                    
                                Laravel Dusk (E2E)
                                
                                                                        Intermediate
                                                                                                            3y
                                                                    
                                Factories / Seeders
                                
                                                                        Advanced
                                                                                                            6y

                            Artificial Intelligence
                        
                                GitHub Copilot
                                
                                                                        Advanced
                                                                                                            3y
                                                                    
                                Cursor
                                
                                                                        Advanced
                                                                                                            2y
                                                                    
                                ChatGPT (OpenAI)
                                
                                                                        Advanced
                                                                                                            3y
                                                                    
                                Claude (Anthropic)
                                
                                                                        Advanced
                                                                                                            2y

05.

Leadership & Strategy

Leadership experience spanning robust backend design, complex integrations, technical team management and system stabilization under critical conditions.

Robust and scalable backend

Design and implement backends that support critical business operations with high availability.

• Built backend of 4 microservices with 120+ models, async orchestration and multi-tenancy at Esfera Médica
• Implemented complete CFDI 4.0 invoicing cycle with async processing reducing >80% manual intervention
• Designed REST API consumed by web and mobile portals for Fundación Lazos (~9,453 active sponsors)

Complex integrations and financial processing

Integrate external services, payment processors and fiscal compliance into automated flows.

• Integrated 3 payment processors with proprietary formats and automatic response reconciliation
• Automated end-to-end CFDI electronic invoicing, delivering roughly 3x better cost efficiency
• Integrated 7+ hardware devices with centralized backend for SAT at national scale

Technical leadership and team management

Lead development teams, establish code standards and guarantee quality deliveries.

• Led teams of 6 and 4 developers in parallel projects at Warriors LABS
• Managed team at Esfera Médica: code review, +25 production releases
• Rebuilt the complete IT engineering area at DR México after massive team resignation

Stabilization and system recovery

Diagnose undocumented systems, resolve critical incidents and guarantee operational continuity.

• Stabilized 10+ legacy projects with heterogeneous stacks at DR México — 100% SLA compliance
• Recovered complete infrastructure after power failure (servers, firewalls, DNS, Docker)
• Maintained continuous microservice ecosystem operation without performance degradation

06.

Resume

Senior backend developer with 10+ years of experience in PHP/Laravel and C#/.NET development. Specialized in APIs, financial integrations, async processing, and event-driven architectures.

10+ years of backend development experience with PHP/Laravel and C#/.NET Backend of 4 microservices in production with 120+ models and async orchestration End-to-end automated CFDI 4.0 invoicing reducing >80% manual intervention Integration with 3 payment processors with proprietary formats and automatic reconciliation Nationwide backend systems — 30,000+ users, 35 offices Open-source package author: 15,017+ installs on Packagist, rated 5.0/5

Open Resume (PDF)

// Education

Computer Engineering
Facultad de Estudios Superiores Aragón — UNAM

                                 – 2015
                                                                GPA: 8.2
                                                            

Accounting (High School)
Colegio de Bachilleres del Estado de México

                                 – 2010
                                                            

// Certifications

Scrum Master

                                Scrum Master Accredited Certification
                                                                2019
                                                                                            

Management Skills Development Diploma

                                Faculty of Engineering, UNAM
                                                                2022
                                                                                            

// Languages

                            Spanish
                            Native
                        

                            English
                            Intermediate–Advanced (fluent technical reading, written and verbal communication)
                        

07.

Let's Connect

Seeking senior backend developer or backend software engineer roles. Open to remote or hybrid work in Mexico City. Specialized in PHP/Laravel, REST APIs, financial integrations, and async processing. Available to start immediately.

Preferred

Email

info@javiiscript.com

https://www.linkedin.com/in/javier-marquez-46ab25367/

GitHub

https://github.com/JaviiScript

// Before we connect

                            ✓
                            Looking for senior backend developer or backend software engineer roles
                        
                            ✓
                            Open to remote or hybrid (Mexico City)
                        
                            ✓
                            Specialized in PHP/Laravel, REST APIs, financial integrations and async processing
                        
                            ✓
                            Experience with distributed teams and agile environments
                        
                            ✓
                            Available to start immediately

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