AWS Lambda's introduction of Durable Functions at re:Invent 2025 has added a powerful new tool for developers. These functions can span up to a year per execution and offer built-in checkpointing. This means that if an execution is interrupted, it can resume from the last completed step, saving time and effort. This feature is particularly useful in complex workflows where multiple AWS services need to be coordinated.

Durable Functions now provide functionality similar to AWS Step Functions, allowing developers to create workflows within the familiar Lambda environment. This could simplify workflow creation and management for those already using Lambda. The new callback feature, for instance, enables human-in-the-loop workflows, where a process can wait for human input before proceeding. This is especially valuable in business processes requiring approvals or reviews.

The blog post illustrates this with a simple leave management system. When an employee submits a leave request, a Durable Function starts an execution that creates a leave record in a DynamoDB table. The employee and manager receive emails, and the function waits for the manager's approval or rejection. If the manager doesn't respond within a set time, the request expires. This example demonstrates the potential of Durable Functions to streamline business processes that require human interaction.

This introduction of Durable Functions is likely to influence how developers approach workflow orchestration, potentially reducing reliance on Step Functions for certain tasks. The ability to integrate human-in-the-loop processes natively within Lambda could lead to more seamless and efficient business workflows.