Java / Java 21 Virtual Threads Interview questions
When should you use virtual threads over platform threads?
Reach for virtual threads when your workload is dominated by waiting rather than computing: handling many simultaneous HTTP requests, calling downstream services, querying databases, or performing file I/O.
They shine in a thread-per-request server design, where each incoming request gets its own virtual thread for its entire lifetime, letting you write plain sequential code that blocks freely without worrying about exhausting OS threads.
If your service currently struggles to scale because a fixed thread pool becomes the bottleneck under concurrent, mostly-idle connections, that's a strong signal virtual threads are the right fit.
Virtual threads are the better fit for workloads that are:
A thread-per-request design with virtual threads means:
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