Higher Technician in Multiplatform Application Development
Progresa Centro de Formación Profesional CIEEP
Gabriel Sánchez Micó
Software EngineerJava Backend · Spring · Oracle · Legacy Modernization
5+ years modernizing and maintaining critical Java applications in production. I diagnose complex issues, design the minimal necessary change, and evolve legacy systems without compromising stability.
About me
Software Engineer specialized in Java backend development, evolutionary maintenance and modernization of enterprise applications, with 5+ years working on production systems within the Java ecosystem.
My work centers on understanding existing applications, pinpointing incidents precisely, building new functionality, and progressively modernizing legacy systems without compromising their stability.
I've worked with Java, Spring Framework, Spring Security, Hibernate/JPA, Oracle, Maven and Tomcat, alongside complementary frontend and integration technologies.
I favor maintainable solutions over impressive ones: I reuse existing architecture before introducing new abstractions, and avoid complexity that doesn't solve a real problem.
Experience
Nunegal Consulting
Software Engineer
Evolved and maintained the Java backend for management and traceability applications. Led the migration from Java 8/Tomcat 8 to Java 11/Tomcat 9, improving performance. Designed security mechanisms with Spring Security, audit trails with Hibernate Envers, and document generation decoupled from the domain. Implemented blockchain integration via smart contracts and collaborated with NestJS/Angular teams.
- Java 11
- Spring Framework 5
- Spring Security
- Hibernate
- JPA
- Oracle
- Maven
- Tomcat 9
- JUnit
- Mockito
- Git/GitLab
Bilbomática, an Altia Company
Software Engineer
Evolved and maintained enterprise Java applications, integrating them with other systems. Contributed to migrating a WordPress site to Magnolia CMS. Took sole ownership of maintaining and evolving a legacy Java 6 application.
- Java 8
- Java 6
- Spring 4
- Magnolia CMS
- WordPress
Capgemini
Software Engineer
Corrective and evolutionary maintenance of enterprise applications: incident investigation, new feature development with Java 8/Spring 4 and JavaScript (jQuery), and integration troubleshooting across systems.
- Java 8
- Spring 4
- Oracle
- SQL
- JavaScript
- jQuery
Health in Code
Software Engineer
Built two applications for processing and writing files derived from DNA sequencing, with an Angular 11 web client for real-time data reading and visualization.
- Java 8
- Spring 4
- Angular 11
Education
Expertise
- Java Backend
- Designing and maintaining services, controllers and repositories with Java and Spring.
- Legacy Modernization
- Progressive migrations (Java 6 → 8 → 11, Tomcat 8 → 9) that preserve compatibility.
- Debugging
- Investigating complex incidents down to their root cause.
- Refactoring
- Improving maintainability and separating responsibilities when there's a clear technical reason.
- SQL / Oracle
- Complex queries, filters, aggregations and optimization on Oracle.
- System Integration
- Integrating Java applications with external services, including blockchain and smart contracts.
- Application Security
- Spring Security: authentication, authorization and request-validation filters.
- Testing
- Unit testing with JUnit and Mockito focused on code quality.
Achievements
Representative milestones from my career.
- Designed periodic processes, judging when a simple scheduled task was enough versus when Spring Batch was justified by data volume.
- Improved file-upload security by validating actual content via binary signature checks, not just file extension.
- Designed document generation decoupled from the domain, supporting multi-page documents and variable data collections.
- Migrated the version-control workflow from SVN to Git/GitLab, adopting branches, releases and tags.
- Maintained applications across four technology generations simultaneously (Java 6/8/11, Spring 4/5, Tomcat 8/9) without losing stability.
- Optimized SQL queries on Oracle for large-volume data analysis and temporal queries.
How I work
When I pick up a feature or an incident, I try not to jump straight into writing code.
Passed
Understand
Understand the real problem and which parts of the system are involved before touching any code.
- Understand the real problem
- Locate which parts of the system are involved
- Review how the project already solves similar problems
- Identify which contracts need to be preserved
Solve
Design the minimal necessary change, reusing what exists and separating responsibilities where it adds value.
- Assess whether reusable code exists
- Design the minimal necessary change
- Separate responsibilities when the change justifies it
- Implement
Improve
Test normal behavior and edge cases, and improve only what genuinely needs it.
- Test normal behavior and edge cases
- Review whether the solution introduces unnecessary complexity
Deploy
The change reaches production without compromising system stability.
- Stable in production
Things I'm proud of
Understand before you change
Software that already exists
I know how to work with software that already exists: understanding applications written by other people, tracing a problem back to its source, and changing only what genuinely needs to change.
- Sole ownership of maintaining a Java 6 application.
- Led the migration from Java 8 to Java 11 and from Tomcat 8 to Tomcat 9.
- Kept legacy applications running in production without compromising stability.
- Designed audit, traceability and security mechanisms with Spring Security.
- Integrated Java applications with blockchain and smart contracts.
Challenges I'm looking for
I find these kinds of problems especially interesting:
This works almost all the time, but fails in specific situations
We have an old system and need to add this feature without breaking what already exists
This part of the code has become hard to maintain
We don't know exactly where this incident originates
This query works, but it's starting to struggle as data volume grows
We need to modernize this application, but we can't rewrite it from scratch
We need to integrate this system with another without fully coupling them
What's next
Areas I'm actively growing in:
- Going deeper into modern language versions after years on Java 6, 8 and 11.
- Architectural decisions at scale: modular monoliths versus independent services.
- Profiling, JVM tuning and systematic bottleneck analysis.
- Concurrency, parallelism and asynchronous processing in the Java ecosystem.
- Evolving toward integration testing, contract testing and Testcontainers.
- Containers, reproducible deployments and observability.
Hire me
I add the most value on Java backend projects: evolutionary maintenance, legacy application modernization, and solving complex problems.
Soft skills
- Ownership
- Took sole ownership of maintaining and evolving a Java 6 application.
- Analytical thinking
- I'd rather find out why something doesn't work than mechanically implement a closed spec.
- Collaboration
- I've solved incidents alongside different technical profiles and worked closely with NestJS and Angular teams.
- Judgment
- If the problem can be solved by touching one component, I don't touch five. Every abstraction has to solve a real problem.
- Open to feedback
- I value code review and technical discussion: decisions get justified, and everyone learns from everyone.
- Adaptability
- I've worked across different technology generations (Java 6, 8 and 11; Spring 4 and 5) and adapt to what each project needs.
Let's talk
Tell me briefly about the project or role and I'll get back to you by email.