Messaging Best Practices

Building reliable messaging systems on Google Cloud requires more than choosing the right service. This lesson consolidates the best practices for Pub/Sub, Cloud Tasks, and Cloud Scheduler into a comprehensive guide covering architecture, reliability, security, performance, cost optimisation, and operational excellence.

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Architecture Best Practices

Choose the Right Service

Requirement	Service
Fan-out events to multiple services	Pub/Sub
Dispatch tasks to a single handler with rate control	Cloud Tasks
Schedule recurring jobs	Cloud Scheduler
High-volume, cost-sensitive streaming	Pub/Sub Lite
Complex stream processing with windowing	Dataflow
Simple event-driven reactions	Cloud Functions + Pub/Sub
Containerised event handlers	Cloud Run + Pub/Sub (push)

Design for Failure

1. Always configure dead-letter topics for production Pub/Sub subscriptions
2. Set appropriate retry policies — distinguish transient from permanent failures
3. Implement circuit breakers in subscribers to prevent cascade failures
4. Use acknowledgement deadline extension for long-running processors
5. Monitor backlog growth and alert before messages expire

Design for Idempotency