Exactly-Once in Spark Structured Streaming: What That Actually Means
Every time I see ‘exactly-once semantics’ in a product README, I add a small mental asterisk. Not because the claim is false (it’s often technically accurate), but because it means something much more specific than most people assume when they first encounter it. I spent the better part of a sprint in our banking platform trying to diagnose why we had duplicate payment records in our Delta Lake tables despite using Spark Structured Streaming with checkpointing enabled. We […]