Dead-Letter Queue

Kind: pattern

Layer: Execution Core

Aliases: DLQ

Record: architecture:dead-letter-queue

Severity: contextual

Scope: service, messaging, resilience

Canonical: Ontology

A design pattern that moves a message which keeps failing into a separate queue, where it can be inspected and reprocessed.

Listed in Architecture principles, after Append-Only Log and before Idempotent Consumer.

Requires

• Message Queue

Reinforces

• Fault Isolation
• Observability

Enables

• Poison-Message Quarantine
• Reprocessing After Fix

Conflicts with

• Infinite Redelivery Loop

In tension with

• Operational Overhead

Tensions

• Dead-Letter Queue / Operational Overhead

Violated by

• Infinite Redelivery Loop

Severity

• contextual

Category

• Event / Messaging / Asynchronous Architecture

Linked from

• Event / Messaging / Asynchronous Architecture
• Observability / Auditability / Traceability
• Event Messaging Async
• Quality Attributes
• Severity levels
• The resolutions