Hire Java developers who ship Spring services that hold up under load

• Your Spring Boot monolith has grown slow, and you need someone to profile it, kill N+1 queries, and carve out services without betting the company on a full rewrite.
• A legacy Java 8 codebase needs to move to a current LTS like Java 17 or 21, so you get virtual threads, records, and dependencies that still receive security patches.
• You are building a high-throughput backend on Kafka and need engineers who understand consumer groups, partitioning, backpressure, and what exactly-once actually costs.
• Production keeps paging you for memory leaks and long GC pauses, and you want someone who reads heap dumps and tunes the JVM instead of just restarting pods.

Every engineer we put forward is screened by a senior Grape5 engineer before you meet them. For Java developers, we look specifically at:

• Concurrency: we hand them shared mutable state and watch whether they reach for the right tool, ConcurrentHashMap, ReentrantLock, or virtual threads, and can explain races, visibility, and deadlocks instead of sprinkling synchronized everywhere.
• Hibernate and JPA: we check that they spot N+1 selects, know when to use a fetch join, entity graph, or projection, and understand the persistence context, lazy loading, and transaction boundaries.
• JVM behavior: we ask them to reason from a GC log or heap dump, choose between G1 and ZGC for a latency-sensitive service, and size the heap and thread pools with a reason, not a guess.
• Spring internals: we probe dependency injection scopes, transaction propagation, and where Spring Boot auto-configuration saves time versus where it hides the bug you are chasing.
• Testing: we look at their JUnit 5 and Mockito habits, whether they test behavior over implementation, and whether they use Testcontainers for database integration tests that mean something.