Victor Tejero Millaruelo

I work at Akkodis as a Backend & Frontend Software Engineer, contributing to the development and maintenance of a railway routing application used across Spain and at a European level, supporting real-time train operations. The system is built with a strong focus on reliability, performance, and concurrency, since it processes live events coming directly from trains and infrastructure. My work is mainly focused on Java and Spring Boot, developing services that run in highly concurrent environments using JMS messaging (AMQ/ActiveMQ), scheduling mechanisms, and multithreading. I regularly validate new features with real operational train data, ensuring the platform remains stable and accurate in production-like conditions. The project is delivered for ADIF, so quality and robustness are essential. One milestone I'm especially proud of happened when I joined the project: the platform was experiencing an intermittent issue where message queues would randomly stop working and the team couldn't reliably reproduce the root cause. I started with an internal investigation, analyzing logs and runtime behavior, and I discovered a clear pattern: the queues that failed were consistently the ones that had been inactive for long periods, meaning they had not received messages for a significant amount of time. Based on that finding, I designed and implemented a fully automatic keepalive mechanism inside the communications library. This included periodic keepalive messages to prevent queues from becoming inactive, and a watchdog component that monitored those signals and marked listeners as healthy whenever keepalive messages were received. The key improvement was that the solution was implemented at library level, making it transparent and invisible across all listeners — around 60 of them — with zero need to modify each listener individually.

Backend Developer in Java, contributing to the maintenance and evolution of the hexagonal architecture supporting Mercadona’s Human Resources systems, including performance evaluation, payroll management in Portugal, and other key corporate processes.

Working within a multidisciplinary team of junior, mid-level, and senior developers, collaborating closely with functional leads and internal teams to ensure software quality, consistency, scalability, and maintainability. Active involvement in the design and development of domain modules, adapters, use cases, business events, and microservices, following Clean Architecture and TDD principles.

Experience developing Java services on Mercadona’s internal framework, applying company-specific security, authentication, and authorization policies. Implementation and maintenance of Kafka topics for data replication and synchronization across corporate applications, ensuring integrity and consistency between systems.

Daily work with relational databases such as Oracle, PostgreSQL and SQL Server, as well as MongoDB and bucket-based storage systems for distributed object and file management. Collaboration with payroll, data, security, operations, QA, SRE teams and external providers to evolve the HR ecosystem.

Hands-on experience with CI/CD using CloudBees, Jenkins Enterprise and Spinnaker, managing automated build and deployment pipelines across integration, pre-production and production environments. Advanced use of GitHub Enterprise, structured branching strategies, pull requests, code reviews, quality checks and pipeline-based workflows.

Regular use of SonarQube for code quality, vulnerability detection and compliance with internal standards. Experience deploying and managing microservices in Kubernetes environments on GCP and AWS, as well as OpenShift on-premise environments, following security, observability, auto-scaling and configuration management best practices.

Backend Developer with experience in designing and developing scalable, maintainable backend architectures using Java and Spring Boot. Developed robust RESTful APIs to manage communication with MariaDB databases, ensuring clean integration between frontend and backend modules.

Worked with JPA/Hibernate for entity mapping, data persistence, complex queries, and optimized data access, focusing on performance, consistency, and data integrity. Implemented complete security solutions with Spring Security, including role-based authentication, JWT tokens, session management, access control, and protection against common vulnerabilities such as CSRF and XSS.

Designed and developed features involving NFC tag reading and writing, as well as QR code generation and scanning, enabling authentication, inventory management, traceability, and real-time access to information.

Developed a complete cross-platform user interface with Flutter, delivering a modern, responsive, and smooth experience across iOS, Android, and Web. Built custom widgets, managed complex application state, and integrated frontend modules with backend services through well-structured REST APIs.

Implemented validations, error handling, and clear API responses to ensure reliability and controlled behavior in unexpected scenarios. Designed and optimized CI/CD pipelines with Jenkins, creating Jenkinsfiles for automated testing and secure deployments while following best branching practices.

Used Docker for application containerization and deployed services in Kubernetes, improving scalability, resilience, and production deployment processes.

Designed and implemented a rigorous testing strategy using JUnit and Mockito for Java, along with widget and integration tests in Flutter, ensuring system reliability and compliance with established quality standards.