Senior Java Backend Engineer - Networking & Data Platform

Senior Software Engineer – Core Java - Java 21 monolith - Remote within Germany

About the Role

Our client is a data integration platform serving more than 2,000 customers, helping them connect business systems, automate workflows, and exchange data across cloud and on-premise environments. Their platform powers supply chains through real-time integration, automation, and intelligent data processing.

The codebase is a Java 21 monolith with no microservices and no Spring Boot. The team uses homegrown frameworks built on top of libraries such as Netty, Jetty, and JPA.

What You'll Do

• Design, develop, test, and maintain production-grade backend software in Java
• Build reliable, scalable, and maintainable platform capabilities
• Contribute to technical design discussions and code reviews
• Debug and optimize complex production systems
• Collaborate closely with Product, QA, and fellow engineers to deliver high-quality releases
• Use AI-assisted engineering tools to improve productivity, automate repetitive work, and enhance software quality
• Take ownership of features from implementation through production

What We're Looking For

• 5+ years of backend Java development
• Strong Core Java skills, including the ability to write Java without the Spring Boot framework
• Experience with concurrency and multithreading
• Experience with JUnit, Mockito, or similar testing frameworks
• Experience with PostgreSQL, Oracle, MySQL, SQL Server, or MongoDB
• Comfortable working in a monolithic codebase

Bonus Skills: Experience in one or more of the following is highly valued and maps to specific teams

• Platform Engineering High availability, load balancing, connection pooling, failover, performance optimization