Create new Lambda function versions and aliases for the development, testing, and production accounts. After successful testing, update the production alias to point to the function. Roll back to the most recent stable function version if issues are discovered.

Deploy the Lambda function to the development, testing, and production accounts separately after successfully testing the function in each environment.

Use Lambda layers to separate the code and the libraries that are associated with each AWS account. Deploy and test the Lambda function with each Lambda layer in each environment.

Update the Lambda function code to use environment variables for the development, testing, and production accounts. Use the environment variables to make code updates available to specific environments.