Activating and managing Lambda SnapStart - AWS Lambda
Activating SnapStart (console)Activating SnapStart (AWS CLI)Activating SnapStart (API)Function statesUpdating a snapshotUsing SnapStart with AWS SDKsUsing SnapStart with AWS CloudFormation, AWS SAM, and AWS CDKDeleting snapshots

Activating and managing Lambda SnapStart

To use SnapStart, activate SnapStart on a new or existing Lambda function. Then, publish and invoke a function version.

Activating SnapStart (console)

To activate SnapStart for a function

  1. Open the Functions page of the Lambda console.

  2. Choose the name of a function.

  3. Choose Configuration, and then choose General configuration.

  4. On the General configuration pane, choose Edit.

  5. On the Edit basic settings page, for SnapStart, choose Published versions.

  6. Choose Save.

  7. Publish a function version. Lambda initializes your code, creates a snapshot of the initialized execution environment, and then caches the snapshot for low-latency access.

  8. Invoke the function version.

Activating SnapStart (AWS CLI)

To activate SnapStart for an existing function

  1. Update the function configuration by running the update-function-configuration command with the --snap-start option.

    aws lambda update-function-configuration \
  --function-name my-function \
  --snap-start ApplyOn=PublishedVersions

  2. Publish a function version with the publish-version command.

    aws lambda publish-version \
  --function-name my-function

  3. Confirm that SnapStart is activated for the function version by running the get-function-configuration command and specifying the version number. The following example specifies version 1.

    aws lambda get-function-configuration \
  --function-name my-function:1

    If the response shows that OptimizationStatus is On and State is Active, then SnapStart is activated and a snapshot is available for the specified function version.

    "SnapStart": { 
    "ApplyOn": "PublishedVersions",
    "OptimizationStatus": "On"
 },
 "State": "Active",

  4. Invoke the function version by running the invoke command and specifying the version. The following example invokes version 1.

    aws lambda invoke \
  --cli-binary-format raw-in-base64-out \
  --function-name my-function:1 \
  --payload '{ "name": "Bob" }' \
  response.json

    The cli-binary-format option is required if you're using AWS CLI version 2. To make this the default setting, run aws configure set cli-binary-format raw-in-base64-out. For more information, see AWS CLI supported global command line options in the AWS Command Line Interface User Guide for Version 2.

To activate SnapStart when you create a new function

  1. Create a function by running the create-function command with the --snap-start option. For --role, specify the Amazon Resource Name (ARN) of your execution role.

    aws lambda create-function \
  --function-name my-function \
  --runtime "java21" \
  --zip-file fileb://my-function.zip \
  --handler my-function.handler \
  --role arn:aws:iam::111122223333:role/lambda-ex \
  --snap-start ApplyOn=PublishedVersions

  2. Create a version with the publish-version command.

    aws lambda publish-version \
  --function-name my-function

  3. Confirm that SnapStart is activated for the function version by running the get-function-configuration command and specifying the version number. The following example specifies version 1.

    aws lambda get-function-configuration \
  --function-name my-function:1

    If the response shows that OptimizationStatus is On and State is Active, then SnapStart is activated and a snapshot is available for the specified function version.

    "SnapStart": { 
     "ApplyOn": "PublishedVersions",
     "OptimizationStatus": "On"
  },
  "State": "Active",

  4. Invoke the function version by running the invoke command and specifying the version. The following example invokes version 1.

    aws lambda invoke \
  --cli-binary-format raw-in-base64-out \
  --function-name my-function:1 \
  --payload '{ "name": "Bob" }' \
  response.json

    The cli-binary-format option is required if you're using AWS CLI version 2. To make this the default setting, run aws configure set cli-binary-format raw-in-base64-out. For more information, see AWS CLI supported global command line options in the AWS Command Line Interface User Guide for Version 2.

Activating SnapStart (API)

To activate SnapStart

  1. Do one of the following:

  2. Publish a function version with the PublishVersion action. Lambda initializes your code, creates a snapshot of the initialized execution environment, and then caches the snapshot for low-latency access.

  3. Confirm that SnapStart is activated for the function version by using the GetFunctionConfiguration action. Specify a version number to confirm that SnapStart is activated for that version. If the response shows that OptimizationStatus is On and State is Active, then SnapStart is activated and a snapshot is available for the specified function version.

    "SnapStart": { 
        "ApplyOn": "PublishedVersions",
        "OptimizationStatus": "On"
     },
     "State": "Active",

  4. Invoke the function version with the Invoke action.

Lambda SnapStart and function states

The following function states can occur when you use SnapStart.

Pending

Lambda is initializing your code and taking a snapshot of the initialized execution environment. Any invocations or other API actions that operate on the function version will fail.

Active

Snapshot creation is complete and you can invoke the function. To use SnapStart, you must invoke the published function version, not the unpublished version ($LATEST).

Inactive

The Inactive state can occur when Lambda periodically regenerates function snapshots to apply software updates. In this instance, if your function fails to initialize, the function can enter an Inactive state.

For functions using a Java runtime, Lambda deletes snapshots after 14 days without an invocation. If you invoke the function version after 14 days, Lambda returns a SnapStartNotReadyException response and begins initializing a new snapshot. Wait until the function version reaches the Active state, and then invoke it again.

Failed

Lambda encountered an error when running the initialization code or creating the snapshot.

Updating a snapshot

Lambda creates a snapshot for each published function version. To update a snapshot, publish a new function version.

Using SnapStart with AWS SDKs

To make AWS SDK calls from your function, Lambda generates an ephemeral set of credentials by assuming your function's execution role. These credentials are available as environment variables during your function's invocation. You don't need to provide credentials for the SDK directly in code. By default, the credential provider chain sequentially checks each place where you can set credentials and chooses the first available—usually the environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN).

Note

When SnapStart is activated, the Lambda runtime automatically uses the container credentials (AWS_CONTAINER_CREDENTIALS_FULL_URI and AWS_CONTAINER_AUTHORIZATION_TOKEN) instead of the access key environment variables. This prevents credentials from expiring before the function is restored.

Using SnapStart with AWS CloudFormation, AWS SAM, and AWS CDK

  • AWS CloudFormation: Declare the SnapStart entity in your template.

  • AWS Serverless Application Model (AWS SAM): Declare the SnapStart property in your template.

  • AWS Cloud Development Kit (AWS CDK): Use the SnapStartProperty type.

Deleting snapshots

Lambda deletes snapshots when:

  • You delete the function or function version.

  • Java runtimes only — You don't invoke the function version for 14 days. After 14 days without an invocation, the function version transitions to the Inactive state. If you invoke the function version after 14 days, Lambda returns a SnapStartNotReadyException response and begins initializing a new snapshot. Wait until the function version reaches the Active state, and then invoke it again.

Lambda removes all resources associated with deleted snapshots in compliance with the General Data Protection Regulation (GDPR).