Manage Lambda function versions

You can use versions to manage the deployment of your functions. For example, you can publish a new version of a function for beta testing without affecting users of the stable production version. Lambda creates a new version of your function each time that you publish the function. The new version is a copy of the unpublished version of the function. The unpublished version is named $LATEST.

Note

To create a new version of your function, you must first make changes to the unpublished version ($LATEST). These changes can include updating the code or modifying the configuration settings. If $LATEST is identical to a previously published version, you won't be able to create a new version until you deploy changes to $LATEST.

After you publish a function version, its code, runtime, architecture, memory, layers, and most other configuration settings are immutable. This means that you can't change these settings without publishing a new version from $LATEST. You can configure the following items for a published function version:

• Triggers

• Destinations

• Provisioned concurrency

• Asynchronous invocation

• Database connections and proxies

Note

When using runtime management controls with Auto mode, the runtime version used by the function version is updated automatically. When using Function update or Manual mode, the runtime version is not updated. For more information, see Understanding how Lambda manages runtime version updates.

Creating function versions

You can change the function code and settings only on the unpublished version of a function. When you publish a version, Lambda locks the code and most of the settings to maintain a consistent experience for users of that version.

You can create a function version using the Lambda console.

To create a new function version

1. Open the Functions page of the Lambda console.

2. Choose a function and then choose the Versions tab.

3. On the versions configuration page, choose Publish new version.

4. (Optional) Enter a version description.

5. Choose Publish.

Alternatively, you can publish a version of a function using the PublishVersion API operation.

The following AWS CLI command publishes a new version of a function. The response returns configuration information about the new version, including the version number and the function ARN with the version suffix.

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

You should see the following output:

{
  "FunctionName": "my-function",
  "FunctionArn": "arn:aws:lambda:us-east-2:123456789012:function:my-function:1",
  "Version": "1",
  "Role": "arn:aws:iam::123456789012:role/lambda-role",
  "Handler": "function.handler",
  "Runtime": "nodejs20.x",
  ...
}

Note

Lambda assigns monotonically increasing sequence numbers for versioning. Lambda never reuses version numbers, even after you delete and recreate a function.

Using versions

You can reference your Lambda function using either a qualified ARN or an unqualified ARN.

• Qualified ARN – The function ARN with a version suffix. The following example refers to version 42 of the helloworld function.

  arn:aws:lambda:aws-region:acct-id:function:helloworld:42

• Unqualified ARN – The function ARN without a version suffix.

  arn:aws:lambda:aws-region:acct-id:function:helloworld

You can use a qualified or an unqualified ARN in all relevant API operations. However, you can't use an unqualified ARN to create an alias.

If you decide not to publish function versions, you can invoke the function using either the qualified or unqualified ARN in your event source mapping. When you invoke a function using an unqualified ARN, Lambda implicitly invokes $LATEST.

Lambda publishes a new function version only if the code has never been published, or if the code has changed from the last published version. If there is no change, the function version remains at the last published version.

The qualified ARN for each Lambda function version is unique. After you publish a version, you can't change the ARN or the function code.

Granting permissions

You can use a resource-based policy or an identity-based policy to grant access to your function. The scope of the permission depends on whether you apply the policy to a function or to one version of a function. For more information about function resource names in policies, see Fine-tuning the Resources and Conditions sections of policies.

You can simplify the management of event sources and AWS Identity and Access Management (IAM) policies by using function aliases. For more information, see Create an alias for a Lambda function.