Senior Java Engineer

Requirements Must have: Strong, hands-on experience with Java 21+ and Spring Boot MVC Solid knowledge of Kafka, PostgreSQL and/or MongoDB Familiarity with Hexagonal / Clean Architectureerns:** Hexagonal Architecture, Microservices, Event-Driven Design, Transactional OutboxSecurity: OAuth2 / JWT, Spring Security, OpenFGATesting: Spock Framework, Testcontainers, WireMock, REST-Assured, ArchUnit, PIT Mutation TestingInfrastrucy proficiency with AI coding tools — Claude Code** is the team standard; experience with agentic development workflows is a strong plus Nice to have: Experience with Spring WebFlux (reactive stack) Familiarity with OpenFGA or similar fine-grained authorisation systems Background in Consumer-Driven Contract testing (Spring Cloud Contract) Senior Software Engineer — Java / Microservices Start date: ASAP Contract type: B2B (145-170pln) Work mode: 100% Remote About the Team You'll be joining a multidisciplinary team of senior engineers within a Consumer & Merchant domain, working on end-to-end parcel creation flows and some of the company's largest technical initiatives. The team operates with high autonomy — engineers have real influence over architectural decisions and drive solutions from analysis all the way to production. The culture is built on knowledge sharing, mutual respect, and engineering excellence, with a genuinely friendly atmosphere. Your Responsibilities Design and implement microservices following Hexagonal Architecture principles within a large-scale distributed system Drive topic analysis and requirement discovery — from business needs to solution architecture and delivery Build and maintain event-driven integrations using Kafka, Avro, and the Transactional Outbox pattern Write comprehensive automated tests: unit, integration, contract (Spock, Testcontainers, Spring Cloud Contract) Participate actively in code reviews and help raise the bar on code quality Work in a CI/CD environment: GitLab CI, Docker, Kubernetes + Helm (GitOps) Use AI-assisted development tools (Claude Code is the team standard) as a primary daily productivity tool — agentic, AI-first development is how this team operates Language & Frameworks: Java 21, Spring Boot 3.x/4.x (MVC & WebFlux), GradleDatabases: PostgreSQL (JPA/Hibernate, R2DBC), MongoDBMessaging: Apache Kafka + Avro + Confluent Schema RegistryPatterns: Hexagonal Architecture, Microservices, Event-Driven Design, Transactional OutboxSecurity: OAuth2 / JWT, Spring Security, OpenFGATesting: Spock Framework, Testcontainers, WireMock, REST-Assured, ArchUnit, PIT Mutation TestingInfrastructure: GitLab CI, Docker, Kubernetes + Helm (GitOps)Observability: Micrometer, Prometheus, SonarQube, CheckstyleAI Tooling: Claude Code (mandatory) / GitHub Copilot / Cursor What Makes This Role Challenging Complex distributed system — dozens of microservices with numerous communication channels; understanding the big picture is as important as writing good code Near-100% uptime requirement — business-critical systems where reliability and fault tolerance are non-negotiable High autonomy from day one — independently analyse topics, identify stakeholders, and deliver solutions end-to-end AI-first way of working — using Claude Code and agentic workflows to accelerate delivery is a core part of how the team operates, not a nice-to-have Requirements: Java, Spring Boot, Kafka, PostgreSQL, MongoDB, Hexagonal, Clean Architecture, OAuth, JWt, Spring Security, OpenFGA, Spock, Testing, AI, Spring WebFlux, Spring Cloud