AWS Lambda Durable Functions: Building Long-Running Workflows in Code

If you've built anything non-trivial on AWS Lambda, you've hit the wall. The function runs for 15 minutes and it's stateless. Any multi-step workflow requires stitching together Step Functions, SQS queues, DynamoDB tables for state, and a whole lot of glue. It works, but it's a lot of infrastructure for what should be straightforward sequential logic. AWS Lambda Durable Functions, launched at re:Invent 2025, change that. You write sequential code in a single Lambda function. The SDK handles checkpointing, failure recovery, and suspension. Your function can run for up to a year, and you only pay for active compute time. During waits (human approvals, timers, external callbacks), the function suspends and compute charges stop. In this post, I'll walk through what problem durable functions solve, how the checkpoint/replay model works, and then dig into a complete AI-powered support ticket workflow in TypeScript that demonstrates every primitive in action. What Problem This Solves Here's a