This is a remote position. Blue Code Alicante is looking for a Freelance Kotlin Developer (remote from Spain is a must) to join a high-ownership engineering team building and evolving a distributed microservices backend on AWS. You'll work across a complex domain that includes route optimization, schedule ingestion, geo-routing and carrier data, all at real scale. You'll take full ownership of services from design to production, drive architectural decisions and proactively identify and fix problems before they become incidents. Responsibilities: Design, build and maintain JVM-based microservices (Java / Kotlin) running on AWS ECS, App Runner and Lambda Work with a rich data layer: PostgreSQL, DynamoDB, RedShift, Redis and S3 Build event-driven integrations via RabbitMQ and SNS Collaborate on API design across REST (API Gateway) and BFF patterns Instrument services with OpenTelemetry, Tempo, Prometheus and Grafana Ship via GitHub Actions CI/CD pipelines with Docker and ECR Work with external integrations including Auth0, GraphHopper, PostHog and Sentry Participate in architecture decisions and technical direction

Requirements

Minimum 6 years of professional backend development in Kotlin / Java Solid understanding of distributed systems design, microservice patterns and event-driven architecture Hands-on production experience with AWS (ECS, Lambda, S3, RDS or DynamoDB) Experience with relational databases (PostgreSQL) and NoSQL (DynamoDB or similar) Strong command of Docker and containerized deployments Experience with CI/CD pipelines (we use GitHub Actions) Clean code as a practice Registered as a freelance in Spain is a must Nice to have (but not required): Experience with message brokers (RabbitMQ, SQS/SNS) Familiarity with observability tooling (OpenTelemetry, Prometheus/Grafana stacks) Background in logistics, routing, geospatial or supply chain domains Experience integrating third-party APIs (auth providers, mapping/routing engines, analytics)

Benefits

Competitive daily or hourly rate, negotiable based on experience / skills International and dynamic work setting Remote work model from Spain Freelance / Contract B2B basis