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Portfolio

SERGIHERRADOR

Backend Software Engineer
Java & Spring Boot Specialist

I design and build resilient backend systems, microservices, and enterprise APIs. Passionate about software architecture, operational stability, and turning complex business domain rules into clean, maintainable code.

View my work→My experience
Sergi's chibi robot mascot
CaixaBank Tech · Backend Engineer
Languages:Spanish (Native)Catalan (Native)English (Fluent)
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About

Sergi Herrador
Name
Sergi Herrador
Location
Barcelona, ES
Role
Backend Engineer
Focus
Java & Spring Boot
Specialization
High-Performance APIs & Microservices

From Android apps
to backend systems.

My journey started with mobile application development and hands-on telecommunications operations, evolving naturally into high-throughput backend engineering. Through every stage, my goal has stayed consistent: craft software that is reliable, elegant, and maintainable.

Academic Grade
9.42/ 10
Final average grade · DAM
Honor Grade / Outstanding
6 / 13 modules · 10/10
Computer Systems10 / 10
Programming10 / 10
Interface Development10 / 10
Mobile & Multimedia Development10 / 10
Service & Process Programming10 / 10
Enterprise Management Systems10 / 10

Professional Experience

Backend systems engineering in real-world environments.

Professional Timeline (2022 – 2026)2022 Presente
CaixaBank Tech logo
current · full-time

CaixaBank Tech

Backend Software Engineer
Barcelona · ES
Sep 2024 – Present (Internship Sep 24 - Jun 25 → Full-time Jun 25 - Present)
  • Joined in September 2024 as an engineering intern and promoted in June 2025 to a permanent full-time position as Backend Software Engineer.
  • Design and evolution of enterprise REST APIs, Event-Driven Architecture, and backend microservices on the JVM with Java 17/21 and Spring Boot 3.
  • Developing high-performance batch processing jobs with Spring Batch and optimizing throughput using Enterprise Caching strategies.
  • Applying Domain-Driven Design (DDD), Clean Architecture, and Value Objects to ensure maintainable, high-quality business logic.
  • Intensive unit and integration testing using Mockito, JUnit 5, and the Object Mother design pattern for clean, robust test suites.
  • Managing production data persistence with Oracle DB, executing advanced SQL queries in SQL Developer, containerizing with Docker, and API testing via Postman.
Core stack
JavaSpring BootSpring BatchAPIs REST
Architecture, Events & Caching
DDDArquitectura LimpiaAPIs EventosCachéOracle DB
Testing & Dev Tools
MockitoMother PatternSQL DeveloperDockerPostman
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Swagger UIv3.0.1
sergi-profile-api
APFutura logo

APFutura

Telecommunications Engineer
previous · role
2022 – 2024 · Spain (Fiber Network Operations for London)

I started at APFutura as an intern, was subsequently hired through a Dual Education Programme, and progressed to full-time Telecommunications Engineer. I provided direct operational support for a major fiber telecommunications network in London. My daily responsibilities included provisioning OLTs (Optical Line Terminals), setting up client services, and managing technical ticketing and incidents. This role established my foundation in production support, analytical troubleshooting, and critical network infrastructure.

Tech stack & operaciones
Fiber NetworkOLT ProvisioningService ActivationTicketing SystemNetwork OperationsSQL
Resumen de Operación
companyAPFutura
roleTelecommunications Engineer
dates2022 – 2024
stackOLT Provisioning · Fiber Services · Ticketing · Network Infrastructure

Selected Work

Crafting software with focus & purpose.

SerGibli

An Android application inspired by Studio Ghibli, built during Sergi's mobile development journey. A love letter to animation, wrapped inside a native mobile experience with Kotlin, Jetpack Compose, Retrofit, and Room.

KotlinAndroidREST APIJetpack ComposeRoom
View project →View code

Android Trivia App

View project →View code

A mobile trivia game with multiple rounds, difficulty selection, a countdown timer, image-based questions, score tracking, dark mode and native sharing.

KotlinAndroidTimerDark mode
Android Trivia App settings in dark mode
Android Trivia App Cowboy Bebop gameplay question
Android Trivia App perfect score results
Interactive gameplay & dynamic scoring

SergiiTB Maps

View project →View code

An Android application focusing on location-based services, integrating map functionalities and geographical data: pins, routes, and coordinates as core elements.

KotlinAndroidGoogle MapsGeolocation
Maps App camera capture
Maps App map view with markers
Maps App create marker view
Google Maps API integration with live geolocation

Barcelona Energy Consumption Analysis

Data analytics and Machine Learning project (SDG 7) built in collaboration with Sergi, Xavi, and Alexandru on real Open Data BCN datasets (2023–2025). Features exploratory data analysis (EDA), BeautifulSoup web scraping, Folium geospatial maps with OpenCage geocoding, Linear Regression for 2025 trend forecasting, and unsupervised KMeans clustering (3 consumption profiles).

PythonPandasScikit-LearnFoliumLinear RegressionKMeans

Tech universe

A stack with a clear center of gravity.

Primary Core StackMain Focus
Java+ Spring Boot
Spring BatchREST APIsDDDClean ArchitectureMicroserviciosOracle DBDockerPostman
Production backend stack powering enterprise-grade systems, microservices, and RESTful web services.
Enterprise BackendPatrones y Herramientas
MockitoJUnit 5Object MotherREST AssuredValue ObjectsAPIs en EventosCaché EnterpriseSQL Developer
Previous Stackprojects · solid background
KotlinAndroidJetpack ComposeFirebaseGoogle Maps APIRoom SQLite
Explorationscuriosity & growth
PythonMachine LearningComputer VisionData AnalysisWeb Scraping

Contact

Let's build something reliable.

Let's talk. Start a conversation.

Did you like what you see? You can keep exploring by dropping me a message or making a POST request in the swagger section!

Say hello →Download CV
email · sergiherrador44@gmail.comlinkedin · in/sergi-herrador-díaz/github · @sergiherradorITB
Sergi's mascot waving
Location: Barcelona, ES
Specialized in Java, Spring Boot & Microservices
sergiherrador44@gmail.com