Senior Java Software Engineer (Distributed systems)

Senior Java Software Engineer (Kafka, Security) – Messaging/Booking – Amsterdam

Hourly rate: €50 - €100

Duration: 12 months

Hybrid or Remote

Start: ASAP

My client is looking for 3 Senior Backend Engineers to join the team on a 12 month contract. As a Backend Software Engineer, you'll design, build, and operate Java-based backend services that power messaging security capabilities. You'll own solutions end-to-end from implementation and testing through deployment, monitoring, and production support.

This role is ideal for a strong backend engineer who enjoys working with distributed systems, APIs, cloud-native technologies, and large-scale messaging infrastructure while solving complex security challenges.

What You'll Do

• Design, develop, and maintain backend services using Java and modern engineering practices
• Build security capabilities that detect and prevent spam, phishing, malicious links, malicious attachments, and messaging abuse
• Work within a large existing Java codebase and contribute to long-term platform improvements
• Design and evolve APIs, ensuring strong developer experience and maintainable integration patterns
• Collaborate with messaging platform teams to integrate security controls into core messaging workflows
• Participate in system design discussions, evaluating solutions for scalability, reliability, and security
• Own services end-to-end, including deployment, monitoring, alerting, troubleshooting, and operational support
• Investigate production incidents, perform root cause analysis, and implement preventative solutions
• Improve service maturity through automated testing, observability, and continuous delivery practices
• Support the migration of legacy consumers from database-driven integrations to modern API-based solutions

Required

• Strong experience building backend applications in Java (Java 17+ preferred)
• Experience developing and operating production services
• Ability to work effectively within large, established codebases
• Experience with microservices and distributed systems
• Familiarity with Kafka or similar messaging/streaming technologies
• Experience designing and consuming REST APIs
• Strong understanding of software engineering best practices, including testing, code reviews, and CI/CD
• Ability to work independently and take ownership of technical solutions
• Professional English communication skills

Preferred

• Spring Boot or DropWizard
• AWS (EKS, S3, and related services)
• Kubernetes
• GitLab CI/CD and deployment orchestration tools
• OpenAPI specifications and API lifecycle management
• Grafana, Loki, OpenTelemetry, and distributed tracing
• Experience with high-throughput messaging systems
• GraphQL
• Security engineering, fraud prevention, abuse detection, or application security experience
• Understanding of spam detection, phishing protection, malicious file scanning, or link security
• Interest in AI/ML applications for security and threat detection