Day 34: Consumer Acknowledgments and Redelivery Mechanisms
What We’re Building Today
Today we implement reliable message processing with intelligent failure handling:
Manual acknowledgment control to prevent message loss during processing failures
Configurable retry mechanisms with exponential backoff for transient errors
Dead letter queues to isolate poison pill messages from healthy traffic
Idempotency tracking to guarantee exactly-once processing semantics
Why This Matters
In distributed systems, message acknowledgment determines whether your system loses data or processes it twice. At scale, the difference is billions of events. When Uber’s payment system processes ride completions, a lost acknowledgment means a driver doesn’t get paid. A duplicate acknowledgment means charging a rider twice. Netflix’s recommendation system processes 500 billion events daily—without proper acknowledgment strategies, their entire pipeline would grind to halt from poison pill messages or cascade into infinite retry loops.
The acknowledgment pattern defines your system’s reliability guarantees. Auto-commit provides at-most-once delivery (fast but lossy). Manual commit after processing gives at-least-once (reliable but potentially duplicate). Transactional commit achieves exactly-once (correct but complex). Production systems trade throughput for reliability based on business requirements—financial transactions need exactness, video view counts tolerate approximation.
