Day 42: Mastering Exactly-Once Processing in Kafka
The Safety Net That Prevents Million-Dollar Mistakes : Week 6: Stream Processing with Kafka | 254-Day Hands-On System Design Series
What We'll Build Today
Banking Transaction Processor - Handles transfers between accounts
Exactly-Once Consumer - Guarantees no duplicate processing
Transactional Producer - Atomic message sending with rollback
Real-Time Dashboard - Monitor transactions and account balances
Failure Recovery System - Handles crashes without data loss
End Result: Production-ready system processing financial transactions with zero duplicates, even during failures.
Picture this: Your banking application processes a $10,000 transfer, but a network glitch causes the consumer to restart mid-processing. Without proper safeguards, that transfer might execute twice, turning a routine transaction into a $20,000 mistake. This nightmare scenario is exactly why exactly-once processing semantics exist in distributed systems.
Today, we're implementing the bulletproof mechanisms that ensure each log entry gets processed exactly once - no more, no less. By lesson's end, you'll have built a system that handles network failures, consumer crashes, and broker restarts without duplicate processing.