Dead letter queue (DLQ) ni mahali ambapo ujumbe huenda wakati hauwezi kuchakatwa au hukidhi masharti fulani (umekataliwa, umeisha muda, queue imejaa). DLQs huzuia ujumbe wenye matatizo kupotea au kuzuia uchakataji, ukiwezesha ukaguzi na ushughulikiaji baadaye.
Dead letter queue ni nini
DEAD LETTER QUEUE → a queue that receives messages that couldn't be delivered/processed
normally:
→ messages are "dead-lettered" (routed to the DLQ) when they:
- are REJECTED/nacked (consumer can't process them) without requeue
- EXPIRE (message TTL exceeded)
- exceed the queue's MAX LENGTH (overflow)
→ the DLQ collects these for inspection/handling instead of losing them
→ a "holding area" for problematic messages
