.NET Architecture & System Design Interview Question #45

What is a dead-letter queue (DLQ)?

Caching, CDN, Queues & Asynchronous Processing Junior Beginner

Quick Interview Answer

A dead-letter queue stores messages that could not be processed successfully after the configured retry or rejection policy. It prevents one repeatedly failing message from blocking normal processing.

Detailed Explanation

DLQs require operational ownership. Teams need monitoring, diagnostics, retention rules, and a safe procedure to fix, replay, or discard failed messages.

Code Example

Main Queue -> Consumer
                |
          repeated failure
                v
          Dead-Letter Queue