AWS Lambda Durable Functions - Build a Loan Approval Workflow with Checkpoints, Callbacks, and a React Frontend

I have been using AWS Step Functions for workflow orchestration for a long time now. I used it in my Serverless Data Processor project to coordinate batch data processing and in the Serverless Cloud Pizzeria to manage pizza order progress with task tokens. Step Functions is a solid service that does a lot of things well, especially when you want visual observability and native AWS service integrations. When AWS announced Lambda Durable Functions at re:Invent 2025, I was immediately curious about how it compared and whether it could handle the kind of workflows I typically build. After spending some time reading the docs, community articles, and building a demo project, I wanted to share what I learned and walk through a working example. The full source for this project can be found here on GitHub: https://github.com/RDarrylR/lambda-durable-demo The Problem with Long-Running Lambda Workflows If you have spent any time building serverless applications on AWS you have likely run into the