5 posts
The final part of the JVM concurrency series. A four-question framework for choosing between Virtual Thread, Reactor, and Coroutines, plus the unique strengths of each technology and the most common misconceptions.
How Spring wraps suspend fun in mono {} to run it on the Reactor pipeline, and the structural limit where AOP proxies mistake COROUTINE_SUSPENDED for method completion — including why @Transactional + coroutines does not work.
Starting from the one-request-one-thread limit of Spring MVC, this post digs into how WebFlux actually works — the Netty event loop architecture, MVC vs WebFlux request handling, and what you must never do on an event loop thread.
From the Pull vs Push model to the four Reactive Streams interfaces, Reactor's Mono/Flux and core operators, and backpressure — building a solid mental model of reactive programming.
Why ThreadLocal-based traceId propagation fails on the WebFlux event loop, and how Reactor Context's bottom-up propagation model solves it — with hands-on examples.