Senior Java Developer; on site

Duration: 6 – 12 months

Hybrid: 3 days per week on site (mandatory)

Start: ASAP

My new client is looking for 2 experienced Senior Java Developers with strong back‑end engineering skills to support the design, development, and optimization of our API‑driven services. This is a freelance/contract role ideal for someone who thrives in a fast‑moving environment, can work independently, and brings deep expertise across Java, modern API architectures, and complementary .NET technologies.

• Architect, develop, and maintain scalable Java-based back‑end services and RESTful APIs
• Collaborate with cross‑functional teams to design efficient system integrations and data flows
• Enhance existing services for performance, reliability, and security
• Contribute to solution design discussions, providing technical leadership and best practices
• Work with .NET components where required to ensure seamless interoperability across platforms.
• Write clean, maintainable, well‑tested code
• Troubleshoot complex issues across distributed systems
• Participate in code reviews and provide mentorship‑level feedback when needed

• 7+ years of professional experience in back‑end development
• Expert‑level proficiency in Java (Java 8+), Spring Boot, and related frameworks
• Strong experience building and consuming RESTful APIs
• Solid understanding of microservices, distributed systems, and cloud‑native architectures
• Hands‑on experience with .NET / .NET Core for service integration or cross‑stack development
• Proficiency with relational and No
  
  SQL databases
• Familiarity with CI/CD pipelines, containerization (Docker, Kubernetes), and Dev Ops workflows
• Strong problem‑solving skills and the ability to work autonomously
• Excellent communication skills and comfort collaborating in remote teams

• Experience with message queues (Kafka, Rabbit
  
  MQ, etc.)
• Knowledge of cloud platforms (AWS, Azure, GCP)
• Exposure to API gateways, authentication/authorization frameworks (OAuth2, JWT)
• Background in high‑availability or enterprise‑scale systems