Freelance Kotlin Developer (Fulltime)

You'll be a core member of a small, high-ownership engineering team building and evolving the distributed microservices backend that powers our app. You'll work across a complex domain – route optimization, schedule ingestion, geo-routing, and carrier data – at real scale, on AWS. This is not a role for someone who waits for specs to land in their inbox. You'll take full ownership of services from design through production, make architectural decisions, and proactively identify and fix problems before they become incidents. What you'll work on 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 and consume 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 – your opinion will carry weight Must-haves: Work permit for Poland 5+ years of professional backend development in Java and/or Kotlin 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, not a talking point – you write code that your colleagues can confidently extend Genuine ability to self-direct: you can take a loosely defined problem, break it down, make decisions, and deliver Strong plus: Kotlin specifically (greenfield services are Kotlin-first) 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) How we work Small team, high trust – no micromanagement, no approval chains for every decision GitHub-centric workflow – PRs, reviews, and automated pipelines keep quality high without bureaucracy Observability-first – we monitor, alert, and fix things before users notice Clean code culture – we refactor, we review, we don't let tech debt compound silently AWS-native – we use managed services where they make sense and containers everywhere else What we offer Competitive salary benchmarked to your market Remote-friendly setup (we care about output, not location) Direct impact on a product used by global logistics professionals every day Work in a genuinely interesting domain – intermodal routing is hard, and the problems are real A lean, senior team where your architecture decisions actually ship Are you the perfect match? Send your portfolio, CV , and a short message about why you’re the perfect match to us Want to know more? Do you have any questions about this position? Feel free to contact our technical lead Sylwester Wieczorkowski ( [email protected] )