Senior Java Software Engineer (Distributed systems)

Senior Java Software Engineer (Kafka, Security) – Messaging/Booking – AmsterdamHourly rate: €50 - €100Duration: 12 monthsHybrid or RemoteStart: ASAPMy 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 DoDesign, develop, and maintain backend services using Java and modern engineering practicesBuild security capabilities that detect and prevent spam, phishing, malicious links, malicious attachments, and messaging abuseWork within a large existing Java codebase and contribute to long-term platform improvementsDesign and evolve APIs, ensuring strong developer experience and maintainable integration patternsCollaborate with messaging platform teams to integrate security controls into core messaging workflowsParticipate in system design discussions, evaluating solutions for scalability, reliability, and securityOwn services end-to-end, including deployment, monitoring, alerting, troubleshooting, and operational supportInvestigate production incidents, perform root cause analysis, and implement preventative solutionsImprove service maturity through automated testing, observability, and continuous delivery practicesSupport the migration of legacy consumers from database-driven integrations to modern API-based solutionsRequiredStrong experience building backend applications in Java (Java 17+ preferred)Experience developing and operating production servicesAbility to work effectively within large, established codebasesExperience with microservices and distributed systemsFamiliarity with Kafka or similar messaging/streaming technologiesExperience designing and consuming REST APIsStrong understanding of software engineering best practices, including testing, code reviews, and CI/CDAbility to work independently and take ownership of technical solutionsProfessional English communication skillsPreferredSpring Boot or DropWizardAWS (EKS, S3, and related services)KubernetesGitLab CI/CD and deployment orchestration toolsOpenAPI specifications and API lifecycle managementGrafana, Loki, OpenTelemetry, and distributed tracingExperience with high-throughput messaging systemsGraphQLSecurity engineering, fraud prevention, abuse detection, or application security experienceUnderstanding of spam detection, phishing protection, malicious file scanning, or link securityInterest in AI/ML applications for security and threat detection