AWS Lambda Python runtime 3.9 EoL

When preparing to upgrade your Lambda functions from Python 3.9 to a newer runtime version, following a structured approach will help ensure a smooth transition. Here are recommendations to help you plan and execute this upgrade safely:

Pre-upgrade Validation Steps:

• Test the upgrade script or process in a non-production environment first
• Review your Lambda functions for Python version-specific code that might behave differently in newer versions
• Back up your Lambda function configurations before making any changes
• Create an inventory of all your Python 3.9 functions across accounts and regions

Compatibility and Breaking Change Considerations:

• After Python 3.9 is deprecated, AWS will no longer provide security updates, technical support, or hotfixes
• Functions using deprecated runtimes may experience degraded performance or issues like certificate expiry
• Deprecated runtimes are provided 'as-is' without warranties and may contain vulnerabilities

Best Practices for Testing, Rollout, and Rollback:

• Implement the upgrade in phases to minimize potential disruptions
• Use function versions and aliases to enable safe deployment with rollback capability
• Consider a tiered upgrade schedule based on function criticality:

• Critical functions: Plan 6-month migration cycles with extensive testing
• Important functions: Align with quarterly release cycles
• Non-critical functions: Upgrade within 30 days of availability

• Verify function behavior after the upgrade to ensure everything works as expected
• Maintain a detailed upgrade calendar and actively monitor AWS deprecation announcements

By following these recommendations, you can ensure a safe transition from Python 3.9 to newer supported runtimes while minimizing risks to your production environment.
Sources
Automated Migration Script for AWS Lambda Python 3.9 End-of-Support | AWS re:Post
Lambda runtimes - AWS Lambda
Managing runtime updates at scale for Lambda | AWS re:Post