Q&A
Q&AWhy is blocking JDBC dangerous inside a Spring WebFlux event loop?
A blocking call occupies a small Netty event-loop pool and stalls unrelated connections.
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Reactive event loops depend on handlers returning promptly. Blocking JDBC parks the event-loop thread while it waits for the database, so many unrelated requests queue behind a few occupied threads. Use a reactive driver end-to-end or isolate unavoidable JDBC work on a bounded worker scheduler and constrain concurrency.