fig.01 — profile

BACKEND & PLATFORM ENGINEER

Auth & security
Data pipelines
Infra & deployments
Architecture & best practices

I build what holds everything else up.

Backend, from code to infrastructure: I design architectures, deploy them myself, and stick around when something breaks.

−83%

infra cost, after migrating hosting

2×

event sourcing engine reused across systems

0→prod

multi-tenant billing designed and shipped

Let's talk ↗ See projects ↓

fig.02

Projects

fig.02.01

Java 21 · Kafka · OpenTelemetry · Maven · LocalStack · Docker · Docker Swarm · Kubernetes · Grafana · Github Actions · AWS

Spool Framework

Modular and event-driven Java framework for data pipelines: from extracting external sources to a queryable data mart. Integrated observability with OpenTelemetry, Prometheus and Grafana, and pluggable adapters for Kafka, S3 and more. Final Degree Project at the University of Las Palmas de Gran Canaria.

Code

fig.02.02

Java · Arquitectura hexagonal · AWS · Docker · Spring Boot

Hospital Event Processing Pipeline

Java application for ingesting and processing hospital events, with hexagonal architecture and SOLID principles. Reduces cloud deployment costs by 97% compared to managed alternatives on AWS.

Code

fig.02.03

Java · AWS · DDD · AWS · Docker · Spring Boot

BookStore

Bookstore on AWS with decoupled Java codebase applying Domain-Driven Design, migrated to an AWS Lambda-compatible architecture in less than an hour.

Code

fig.02.04

Kotlin · Jetpack Compose · Clean Architecture · MVVM · Docker

WhereWhen

Mobile application to discover, create, and share nearby social events in real time, with interactive map, live chat, and push notifications. Built with Kotlin, Jetpack Compose, and Clean Architecture + MVVM.

Code

fig.02.05

Java

Bounce Ball Simulator

Physical simulator of a bouncing ball: creation and interactive dragging of balls, freeze the simulation and adjust attributes in real time.

Code

fig.02.06

Java · MVP · Patrones de diseño

MineSweeper

Own version of the classic Minesweeper in Java, developed for Software Engineering II with Model View Presenter architecture and design patterns to make it fully scalable. Three-person team project.

Code

fig.03

Experience

Jun 2026 · present

Workfactory

Backend Engineer

Designed the product's core systems: multi-tenant, consumption-based billing with event sourcing, and a task assignment engine.
Built the booking and guest-communication flow: report delivery via SES, pre-checkin reminders, and automated upsell of extra services.
Reused the event sourcing engine from my thesis (Spool Framework) to build Workfactory's analytics system.
Built end-to-end observability with Grafana and Langfuse, with Slack alerts and automated voice calls for the on-call team.
Led the migration from Railway to a self-managed VPS with Docker Swarm and Dokploy, wiring the VPS Grafana to the dev environment over a private network to keep it off the public internet — cut costs from about €100 to €17 a month.
Introduced GitHub Actions, SonarQube and pre-commit hooks across the team's projects; now leading a large refactor of the codebase and mentoring on scalability and best practices.

Feb 2026 · May 2026

AIDA · Aplicaciones Informáticas Domingo Alonso

Backend Development Intern

Co-developed Data Collector, a three-module system for distributed data collection across every client tenant.
Built a remote agent with access to local databases, periodic polling and chunked result transfers.
Used Azure Blob Storage for persistence and OpenTelemetry for tracing, with authentication via Microsoft Entra ID.
Wrote the Dockerfiles and CI/CD pipelines that deployed to Kubernetes.

fig.04

Skills

Systems & architecture

I design services that scale and can change without fear.

Hexagonal architecture
Microservices
DDD
Event Sourcing
CQRS
SOLID
Clean Code

Data & pipelines

From ingestion to analytics, with end-to-end traceability.

Kafka
PostgreSQL
MySQL

Infra & cloud

From container to production, no surprises.

Docker
Docker Swarm
Dokploy
Kubernetes
AWS
Azure
Blue-Green Deployment
Parallel Change

Observability & quality

If something breaks, I know before the customer does.

Grafana
OpenTelemetry
Langfuse
SonarQube
JUnit
Testcontainers
GitHub Actions
Pre-commit hooks

Languages

Java
TypeScript
Python
JavaScript
C#
SQL
Bash
Go

Education

Sept 2026 · ongoing

Master's in Intelligent Systems and Numerical Applications in Engineering

Universidad de Las Palmas de Gran Canaria

2022 · 2026

Bachelor's in Computer Engineering

Universidad de Las Palmas de Gran Canaria

Honors in key subjects: Web Programming, Software Engineering, Cloud Computing, Programming and Data Structures, and Native Mobile Application Development, plus the thesis.

fig.05

Contact

A system to fix, a team to join, or something half-built? Let's talk.

[email protected]

GitHub

javcastilla

After hours

Poem

An event outside the system: when backend meets poetry. I like writing, so here's something different.

event #001 · type: memoria.append

No hay borrado en mí, solo un registro: cada instante vivido queda anotado, un evento más al final del libro. Nada se pierde. Todo queda guardado.

event #002 · type: memoria.append

Lo que soy hoy no es más que la lectura de todo lo que un día fue escrito. Mi estado actual, mi arquitectura, es solo el eco de lo ya vivido.

event #003 · type: memoria.append

Y si algún día cambio en silencio, de un color a otro, sin ruido ni herida, seguirá el mismo hilo, el mismo comienzo: un registro que no se detiene en la vida.

event #004 · type: memoria.append

No busques una foto, un solo instante, si quieres saber, de verdad, quién soy: soy la suma de todo lo restante, un registro que sigue, hacia delante, hoy.