AWS Lambda – Cold Starts & Provisioned Concurrency

Cold Start

• Happens when AWS creates a new execution environment for a Lambda function.

• Involves loading the code package and running initialization code (outside the handler).

• Large dependencies, heavy SDKs, or complex initialization increase latency.

• Only the first invocation on a new environment is affected; subsequent requests on the same environment are warm starts (no extra init delay).

Provisioned Concurrency

• Pre-warms a set number of Lambda environments so they’re ready before invocation.

• Eliminates cold start latency for all requests.

• Managed via Application Auto Scaling, triggered by schedule or utilization metrics.

Additional Notes