Modern backend services rarely perform isolated work. A single request often fans out into multiple network calls, database queries, and asynchronous operations.
The service is effectively coordinating work under a deadline. That makes concurrency, cancellation, timeout propagation, and failure containment part of the product behavior, not just implementation detail.
Java 21 gives backend teams better primitives for this style of work, especially when concurrency must remain readable and operationally predictable.
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