Senior Java Engineer / Mateusz Król
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
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Design and implement microservices following Hexagonal Architecture principles within a large-scale distributed system
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Drive topic analysis and requirement discovery - from business needs to solution architecture and delivery
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Build and maintain event-driven integrations using Kafka, Avro, and the Transactional Outbox pattern
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Write comprehensive automated tests: unit, integration, contract (Spock, Testcontainers, Spring Cloud Contract)
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Participate actively in code reviews and help raise the bar on code quality
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Work in a CI/CD environment: GitLab CI, Docker, Kubernetes + Helm (GitOps)
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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
Tech Stack
Language & Frameworks: Java 21, Spring Boot 3.x/4.x (MVC & WebFlux), Gradle
Databases: PostgreSQL (JPA/Hibernate, R2DBC), MongoDB
Messaging: Apache Kafka + Avro + Confluent Schema Registry
Patterns: Hexagonal Architecture, Microservices, Event-Driven Design, Transactional Outbox
Security: OAuth2 / JWT, Spring Security, OpenFGA
Testing: Spock Framework, Testcontainers, WireMock, REST-Assured, ArchUnit, PIT Mutation Testing
Infrastructure: GitLab CI, Docker, Kubernetes + Helm (GitOps)
Observability: Micrometer, Prometheus, SonarQube, Checkstyle
AI Tooling: Claude Code (mandatory) / GitHub Copilot / Cursor
Requirements
Must have:
- Strong experience with Java 21+ and Spring Boot MVC
- Hands-on knowledge of Kafka, PostgreSQL and/or MongoDB
- Familiarity with Hexagonal / Clean Architecture and microservices patterns
- Experience with automated testing (Spock or JUnit, Testcontainers, contract testing)
- Proficiency withKubernetes, Helm, and GitLab CI pipelines
- Solid understanding of OAuth2/JWT -based security
- Mandatory proficiency with AI coding tools - Claude Code is the company standard; experience with agentic development workflows is a strong plus
Nice to have:
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Experience with Spring WebFlux (reactive stack)
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Familiarity with OpenFGA or similar fine-grained authorisation systems
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Background in Consumer-Driven Contract testing (Spring Cloud Contract)
What Makes This Role Challenging
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Complex distributed system - dozens of microservices with numerous communication channels; understanding the big picture is as important as writing good code
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Near-100% uptime requirement - business-critical systems where reliability and fault tolerance are non-negotiable
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High autonomy from day one - independently analyse topics, identify stakeholders, and deliver solutions end-to-end
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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
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