What changes would you make when migrating an existing platform-thread codebase to use virtual threads?

The migration generally follows several concrete steps. First, replace fixed thread pools used for I/O-bound work, such as Executors.newFixedThreadPool(200), with Executors.newVirtualThreadPerTaskExecutor(). In a Spring Boot application, this can often be turned on with a single property, spring.threads.virtual.enabled=true. Next, hunt for thread pinning by running the application with -Djdk.tracePinnedThreads=full, and fix any spots where a synchronized block wraps blocking I/O by replacing it with ReentrantLock, which supports unmounting a virtual thread properly. Where practical, replace ThreadLocal usage with ScopedValue, since it scales much better to large numbers of virtual threads. Database connection pools like HikariCP generally don't need to grow -- a modest pool size such as the default of 10 remains appropriate, since making the pool artificially large just wastes database connections without actually improving throughput. Importantly, virtual threads themselves should never be pooled, since they're intentionally cheap to create fresh each time. Finally, genuinely CPU-bound work should remain on a bounded platform-thread pool rather than being moved to virtual threads, since virtual threads offer no benefit for computation that doesn't block.