Answer
Synchronous middleware: Blocks thread while executing.
Asynchronous middleware: Uses Task and await to release thread during I/O operations.
Async middleware improves scalability in high-load systems.
Quick Answer
Synchronous middleware blocks the thread for its duration. Async middleware uses async/await to release the thread during I/O waits. Use async middleware for any I/O in the pipeline (logging to a service, reading from Redis, DB calls). Synchronous middleware in async pipelines can cause thread pool starvation under load. Always write middleware as async unless it has no I/O.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ