At re:Invent 2025, AWS added a new primitive to Lambda called durable execution. Your function can now checkpoint its progress, survive failures without restarting from scratch, and suspend for up to a year without paying for compute time. If you've used Azure Durable Functions or Temporal, the concept is familiar. If you haven't, the short version is that your Lambda function can pause mid-execution, wait for something external (a human approval, a webhook, a scheduled delay), and resume exactly where it left off. No DynamoDB state table. No Step Functions state machine. Just code. This post covers what it is, how it works, when to use it instead of Step Functions, and what it actually looks like to build with. The Problem It Solves Standard Lambda functions run from start to finish in a single invocation. Maximum 15 minutes. If something fails at step 7 of 10, you retry the whole thing.…