Diego Barrio Hortigüela
Senior Backend Engineer · Java, Spring & Applied AI
Cloud-native systems · Distributed architectures · RAG and agentic workflows
Alicante, Spain diegobarrioh@gmail.com LinkedIn diegobarrioh.dev backendtothefuture.com
About
Senior Backend Engineer with over 15 years of experience designing and building distributed systems, payment platforms, and cloud-native applications. Specialized in Java, Spring Boot, event-driven architectures, and microservices, with hands-on experience operating containerized workloads on Kubernetes. Experienced in fintech, banking, and mobility domains, delivering scalable and resilient backend systems. Currently focused on Platform Engineering, Observability, and AI-powered development workflows, exploring agentic systems, LLM integrations, and modern software delivery practices.
Core Competencies
Backend Engineering
Software Architecture
Platform Engineering
Observability
Data & Messaging
AI Engineering
Featured Projects
Akademia
RAG-Powered Learning Platform
Web app to study and prepare for exams. The core of the system is the RAG generation pipeline: it turns the resources a user uploads into tests and questions automatically.
- RAG generation pipeline that produces tests and questions from user-supplied material.
- Embeddings through the OpenAI embeddings API via OpenRouter; Gemini Embedding 2 support in progress.
- Chunking, indexing, and retrieval tuned so generated questions stay grounded in the source.
- Spaced-repetition flashcards and self-assessment.
- Integrated Stripe store to purchase study materials.
Technologies: Java, Spring Boot, PostgreSQL, RAG, OpenAI Embeddings, OpenRouter, Stripe
TokenMeter
Tokenization & LLM Cost Exploration
An open project exploring tokenization and the real cost of LLMs in code generation, across both agentic loops and more direct single-shot flows.
- Repository token analysis engine.
- Cost comparison of agentic versus direct code-generation flows.
- Token counting with the jtokkit o200k_base encoder rather than a character-based approximation.
- Deployed behind Cloudflare.
Technologies: Java, Spring Boot, Docker, Cloudflare, LLM APIs
Forma
Personal Fitness Operating System
A personal health and fitness planning system that connects body composition, training, nutrition and shopping cost into one weekly decision loop.
- Hexagonal backend with a framework-free domain: JDBC and Flyway over PostgreSQL, no ORM, decided and recorded in an ADR.
- LLM-generated nutrition plans are fenced by a validated contract: a plan may only reference food identifiers the API publishes, and anything the model invents is rejected on import.
- Withings OAuth integration for automatic body-measurement sync.
- Weekly insights service that turns raw metrics into small, actionable adjustments.
- React 19 front end with Vitest unit tests and Playwright end-to-end coverage, all gated in CI.
- Spec-driven delivery: 13 architecture decision records and per-story specs kept in the repository.
Technologies: Java 21, Spring Boot 3, PostgreSQL, Flyway, React 19, TypeScript, Vite, Playwright, Docker Compose
Backend to the Future
Engineering Blog & Technical Platform
Personal platform where I publish projects, technical articles, and engineering experiments.
- Backend development.
- Software architecture.
- Cloud-native systems.
- Kubernetes.
- AI engineering.
- Developer productivity.
Local AI Lab
Self-Hosted AI Infrastructure
Personal environment dedicated to evaluating and operating local Large Language Models.
- Local LLM deployment.
- Ollama and LM Studio.
- Models tested: Qwen 3.5, Gemma 3, Llama 3.1, DeepSeek R1, and Mistral Nemo.
- Agentic software development workflows.
- MCP integrations.
- Autonomous coding assistants.
Hardware: NVIDIA GeForce RTX 3060 (12 GB VRAM)
Professional Experience
Senior Backend Engineer
- Designed and implemented billing and payment APIs using Spring Boot, microservices, AWS, and Kubernetes.
- Integrated Apache Kafka to support event-driven architectures and asynchronous processing.
- Promoted Domain-Driven Design, Hexagonal Architecture, and TDD practices.
- Improved CI/CD pipelines using GitLab.
- Contributed to cloud-native platform initiatives and observability practices.
Technologies: Java, Spring Boot, Kafka, Kubernetes, AWS, GitLab CI/CD, Oracle
Senior Analyst
- Developed and maintained banking systems using Spring Boot and Hibernate.
- Built microservices focused on scalability and reliability.
- Managed batch processing workflows using IBM Tivoli Workload Scheduler.
- Optimized complex Oracle and SQL Server queries.
Technologies: Java, Spring Boot, Oracle, SQL Server, IBM Tivoli
Senior Specialist
- Developed and maintained enterprise platforms used across multiple departments.
- Built applications using Spring MVC, WebFlow, JPA, and Hibernate.
- Participated in integrations involving .NET and SharePoint solutions.
Technologies: Java, Spring MVC, Hibernate, Oracle, SharePoint
Analyst
- Developed internal business applications using the Spring ecosystem.
- Participated in the design and implementation of web-based enterprise solutions.
Technologies: Java, Spring, Thymeleaf, Oracle
Analyst & Developer
- Developed and maintained online banking applications.
- Participated in ATM services and core banking migration projects.
Technologies: Java EE, Oracle
Web Developer
- Developed dynamic web applications and interactive user interfaces.
Technologies: PHP, MySQL, JavaScript
Education
Master's Degree in Web Applications and Services Development
Certificate in Java Enterprise Development
Computer Engineering Degree
Equivalent to MSc level under the Bologna Process.
Community & Personal Projects
- Creator of Backend to the Future, a platform focused on software architecture and backend engineering.
- Creator of Akademia, a learning platform whose core is a RAG pipeline that generates exams from user-supplied material.
- Creator of TokenMeter, an open exploration of tokenization and LLM cost in code generation.
- Creator of Forma, a personal fitness operating system where LLM-generated plans are constrained by a validated domain contract.
- Active experimentation with local LLMs, AI agents, and autonomous development workflows.
- Former mentor for Computer Science students through Fundación Banco Sabadell.
Learning Focus
Languages
| Language | Level |
|---|---|
| Spanish | Native |
| English | Full Professional Proficiency (C1) |