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Borja CastroBC

Borja Castro

Backend Engineer & Platform Owner

€350/day
Madrid, ES
3-7 years

Average response time: 1 hour

About Borja

  • Spanish

    Native or bilingual

  • English

    Fluent

Remote only
Primarily works remotely

Experience

  • Lexer
    Backend Engineer & Platform Owner
    September 2025 - Today (10 months)
    Madrid, Spain
    ⋄ Sole technical owner of a Django-based legal document platform handling
    thousands of daily transactions, bridging development and infrastructure. ⋄ Investigated a critical PostgreSQL incident: identified connection saturation
    (520+ connections) caused by Pgpool-II misconfiguration, with hundreds of
    stalled transactions — coordinating the fix with the infrastructure team. ⋄ Optimised slow queries using pg_stat_statements: rewrote NOT IN
    subqueries to NOT EXISTS and inserted indexes with CREATE INDEX CONCURRENTLY with zero downtime. ⋄ Built a centralised observability stack (Loki + Promtail + Grafana) and re
    placed TimedRotatingFileHandler with concurrent-log-handler to elim
    inate log rotation race conditions in production. ⋄ Refactored legacy Django codebase: decoupled business logic and de
    livered new features without disrupting live operations.
  • IGNIS Energía
    Backend Developer
    September 2022 - September 2025 (3 years)
    Madrid, Spain
    ⋄ Designed and implemented a backend system for automated invoice
    processing with automatic field detection and validation — automating 150+
    monthly invoices and eliminating manual accounting workflows. ⋄ Built SAP RFC integrations to extract financial data in real time, streamlining
    reporting and improving visibility of critical business data. ⋄ Designed and deployed an internal ticketing application centralising re quest management across 6 departments, replacing scattered email work flows and improving response times. ⋄ Migrated core database from MySQL to PostgreSQL, managing data integrity
    and minimising operational risk during transition.

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Education

  • CKAD certification.
    CKAD certification.
  • Anonimous-Med
    Universidad ReyJuan Carlos
    2025
    Anonimous-Med

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