Effective August 1, 2025, AWS will standardize billing for the initialization (INIT) phase across all AWS Lambda function configurations. This change specifically affects on-demand invocations of Lambda functions packaged as ZIP files that use managed runtimes, for which the INIT phase duration was previously unbilled. This update standardizes billing of the INIT phase across all runtime types, deployment packages, and invocation modes. In this post, we discuss the Lambda Function Lifecycle and upcoming changes to INIT phase billing. You will learn what happens in the INIT phase and when it occurs, how to monitor your INIT phase duration, and strategies to optimize this phase and minimize costs.
Effective August 1, 2025, AWS will start billing for compute used during INIT phases. No more doing lots of work in your init phase for free
This just means more people will set up Eventbridge rules to call lambdas regularly and keep them running. You avoid having to pay the time penalty and now, actual financial cost of a cold start.
Yeah I often see devs come up with complex architectures to just work around Lambda’s limitations. Things to keep them warm (but then fail because they don’t account for concurrent requests still hitting cold starts), multiple levels of Lambda functions to work around 15 minute time outs, and more. Just use the right tool for the job and look at Fargate or Batch.
This just means more people will set up Eventbridge rules to call lambdas regularly and keep them running. You avoid having to pay the time penalty and now, actual financial cost of a cold start.
Ah yes, keeping your Lambda functions running, rendering the main benefit of them pointless 🙃
People really should just set up a Fargate task instead…
Yeah I often see devs come up with complex architectures to just work around Lambda’s limitations. Things to keep them warm (but then fail because they don’t account for concurrent requests still hitting cold starts), multiple levels of Lambda functions to work around 15 minute time outs, and more. Just use the right tool for the job and look at Fargate or Batch.