Message Queue Patterns

Async service-to-service communication. Not the same as WebSockets (client push) or BullMQ (in-process jobs).

When to Activate

• Decoupling services that don't need synchronous responses
• Building event-driven architectures or CQRS pipelines
• Handling traffic spikes with backpressure (queue absorbs bursts)
• Coordinating cross-service workflows without direct coupling
• Choosing between SQS, Kafka, RabbitMQ, or BullMQ
• Implementing idempotent consumers to handle at-least-once delivery without corrupting state on duplicate messages
• Designing dead-letter queues and replay strategies to recover from poison-pill messages without blocking the main queue

Technology Decision Tree