Developed and integrated REST APIs with external payment services (Telepagos and Agilpagos), including authentication, production error handling, and technical coordination with both companies' teams. Implemented automation scripts for balance reconciliation, reducing the operational load on the internal team. Worked with Redis task queues for background processing and high concurrency management. Resolved race condition issues and optimized async/sync flows to improve response times for critical endpoints. Configured and maintained production infrastructure: Nginx (reverse proxy), Gunicorn (WSGI), systemd, and application deployment. Integrated Oracle databases into existing flows; administered and optimized MySQL schemas. Implemented structured logging, database triggers, and authentication against multiple external services. Containerized applications with Docker and managed versions with Git in collaborative workflows. Wrote technical documentation for APIs, service architecture, and deployment procedures.