Open to opportunities

Jose Carlos User

@josecarlosuser

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Backend developer focused on scalable microservices, reactive systems, and performance-focused engineering.

Spain

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What I'm looking for

I’m looking for a backend role where I can build scalable microservices and reactive systems, optimize performance, and improve reliability through strong test coverage and CI/CD automation—contributing to products with clear engineering standards and growth.

I’m a backend developer who builds scalable, reusable REST services and event-driven systems with a strong focus on performance, stability, and maintainability. I apply SOLID principles to reduce code complexity and make future development easier.

At VOIS (Apr 2025–Present), I improved microservices performance and stability using Spring WebFlux, reducing response times under high load. I also increased test coverage from ~85% to 90% in critical flows, improving release confidence and reducing production issues.

Previously at TMC and Deloitte, I optimized complex database queries across DB2 and Oracle (with CI/CD and analytics support), cutting execution times by over 50% and improving data consistency in inventory and billing processes. I’ve worked with Spring Boot, Hibernate, MyBatis, Kafka, and Reactive Programming, building REST services and Kafka-based systems to increase decoupling and scalability.

Across earlier roles (Sngular, Novanotio S.L., and Common Management Consultant S.L.), I delivered backend APIs for KPI-driven platforms, accelerated data loading by optimizing SQL and database functions, and strengthened legacy modernization efforts. I’m also supported by a Master in Data Science and advanced DevOps & Cloud training, which reflects my drive to pair strong backend engineering with reliable automation and cloud-ready delivery.

Experience

Work history, roles, and key accomplishments

Current

Specialist Software Engineer

Current

Vois

Apr 2025 - Present (1 year 2 months)

Improved microservices performance and stability with Spring WebFlux, reducing response times under high load. Increased test coverage in critical flows from ~85% to 90% and supported team ramp-up by sharing backend best practices.

Webflux Microservices Reactive Programming REST APIs Test Coverage SOLID Performance Optimization System Stability

Software Developer

Tmc

Dec 2023 - Apr 2025 (1 year 4 months)

Optimized complex database queries across DB2 and Oracle, reducing execution times by over 50% and improving data consistency for downstream systems. Developed scalable REST services using SOLID principles, strengthening maintainability and reducing technical debt.

Java Hibernate MyBatis Kafka SQL Query Optimization REST APIs CI CD Snowflake Kubernetes Reactive Programming

Software Developer

Deloitte

Apr 2022 - Dec 2023 (1 year 8 months)

Built and maintained REST services and event-driven systems with Kafka to improve decoupling and scalability. Strengthened delivery reliability by automating testing and CI/CD, reducing manual intervention.

RESTful Services Kafka Event Driven Architecture SOLID Automated Testing CI CD AWS GCP Microservices

Software Developer

Sngular

Mar 2020 - Apr 2022 (2 years 1 month)

Optimized SQL queries and database functions, reducing execution times by over 80% and improving application responsiveness. Built backend APIs for a KPI-driven platform to improve data availability and user visibility, while increasing code quality through higher test coverage.

SQL Optimization Database Performance Tuning Backend KPIs API Development Test Coverage Code Quality Performance Optimization

Professional Programmer

Novanotio S.L.

Sep 2019 - Mar 2020 (6 months)

Improved batch processing performance and data ingestion reliability for large-scale datasets by optimizing data loading. Contributed to legacy system modernization, improving performance and maintainability.

Batch Processing Data Ingestion ETL SQL Query Optimization Data Loading Legacy Modernization Performance Tuning

Junior Consultant

Common Management Consultant S.L.

Sep 2017 - Sep 2019 (2 years)

Developed and enhanced features for a healthcare application, improving usability and system reliability. Supported stable and efficient patient data management through backend improvements.

Backend Development System Reliability Usability Data Management