Sergio Pacheco

Senior Java Backend Engineer with extensive experience in enterprise-scale systems, integrations, and PostgreSQL performance. Specialist in modernizing complex legacy platforms and migrating them to modern stacks (Java 21 / Jakarta EE 10). Proven high-output contributor (#2 in commits for a nationwide ERP) with a focus on code maintainability and reliability.

Strong background in English-speaking professional environments (UK based for 3+ years). Currently based in Granada, Spain, looking for an initial local or international opportunity.

Senior Java Developer at SENAI Soluções Digitais (2021-01 – Present)

One of the world's largest vocational training and technology networks. SENAI Soluções Digitais develops the core ERP (SGN3) managing nationwide educational and financial operations.

• Platform Modernization: Technical lead for the migration of a 500k+ LOC ERP to Java 21 and Jakarta EE 10. Refactored persistence layers and resolved complex HQL/JPQL and WildFly 39 compatibility issues.
• Architectural Governance: Implemented ArchUnit to enforce structural integrity across the monolith. Developed automated rules to govern SLSB state management, CDI scopes (OmniFaces), and serialization patterns, preventing architectural erosion.
• High-Volume Delivery: Ranked as the #2 individual contributor in a codebase with 33k+ commits. Delivered 227k+ productive lines of code and successfully decommissioned 107k+ lines of legacy debt.
• AI-Assisted Engineering: Architected a full-stack AI infrastructure (14 custom MCP servers) to bridge LLMs with enterprise context. Integrated ArchUnit steering rules into AI agents to ensure generated code is compliant with "Hard Contracts" before reaching CI/CD.
• Developer Tooling: Developed a custom IntelliJ Plugin (Kotlin) to eliminate context-switching between the IDE and AI agents. Implemented automated quality gates (DoR/DoD) and adversarial review loops to stabilize delivery.
• Performance & Ownership: Optimized native SQL workflows, reducing execution times by over 60%. Architected 5+ core modules (Assessment, Finance, Special Education) managing the full lifecycle from DB modeling to FreeMarker and PrimeFaces UI.

Full-Stack Developer at Tax Returns Accountants Ltd (2008-04 – 2011-12)

• Developed and maintained an internal tax-refund management system using PHP and MySQL.
• Collaborated in an English-speaking professional environment, focusing on workflow automation and data accuracy for financial services.

IT Director & Lead Developer at Early Career: Mission-Critical Systems

Mainframe Era

• Managed critical service continuity and Y2K strategic planning for municipal and parliamentary systems.
• Built core business logic on high-availability Mainframe environments (Unisys/COBOL), establishing a deep foundation in mission-critical enterprise systems.

Postgraduate Specialist in Distributed Software Architecture – PUC Minas (2024)

Higher Education Degree in Internet Systems Technology – IFRN (2019)