What Is AWS Lambda Runtime?

An AWS Lambda runtime is the environment that executes your function code.
It includes:

- The programming language version (e.g., Python 3.9 or 3.11)
- The AWS SDK (boto3)
- System libraries and environment configurations

When AWS releases new runtimes, older ones are eventually deprecated.
This means they stop receiving security updates, and AWS removes support for them.

Why You Should Change Your Python Runtime

Here are the top reasons to update your Lambda Python runtime:

1. Deprecation of Older Versions

AWS periodically deprecates older Python runtimes.
Once deprecated, you can’t

- Update or redeploy your Lambda function
- Create new functions using that version
- Rely on AWS for bug or security fixes

For example, Python 3.7 was deprecated in December 2023.

2. Security & Stability

Newer runtimes include important security patches and bug fixes.
Using an outdated runtime increases the risk of vulnerabilities.

3. Improved Performance

Newer versions of Python and Lambda offer faster cold start times, optimized memory usage, and better concurrency.

4. Library & SDK Compatibility

Many popular libraries (like NumPy, Pandas, Requests, etc.) drop support for older Python versions.
Upgrading ensures your dependencies continue to work smoothly.

5. Long-Term Maintenance

Staying on a supported runtime ensures that your function remains compatible with AWS updates and new SDK features.

Currently Supported Python Runtimes (as of 2025)

Runtime	Python Version	Status
Python 3.7	Python 3.7	❌ Deprecated
Python 3.8	Python 3.8	❌ Deprecated
Python 3.9	Python 3.9	⚠️ Supported but aging
Python 3.10	Python 3.10	✅ Supported
Python 3.11	Python 3.11	✅ Latest & Recommended

Always use the latest stable version (Python 3.11) for best results.

How to Check Your Current Runtime

You can check your runtime using either the AWS Console or the AWS CLI.

In the AWS Console:

1. Go to the AWS Lambda Console.
2. Select your function.
3. Scroll to Runtime settings—you’ll see your current version (e.g., python3.9).

Using AWS CLI:

aws lambda get-function-configuration \

–function-name MyLambdaFunction \

–query ‘Runtime’

How to Change AWS Lambda Python Runtime

You can update the runtime in two main ways:

🔹 Option 1: Using the AWS Console

This is the simplest way for most developers.

1. Open the AWS Lambda Console
2. Choose your Lambda function
3. Scroll down to Runtime settings
4. Click Edit
5. Under Runtime, select your desired version (e.g., Python 3.11)
6. Click Save

🔹 Option 2: Using AWS CLI

If you prefer the command line, use this command:

aws lambda update-function-configuration \

–function-name MyLambdaFunction \

–runtime python3.11

AWS will confirm the update with a response like:

{

“FunctionName”: “MyLambdaFunction”,

“Runtime”: “python3.11”,

…

}

It may take a few seconds for the update to apply.

Testing After the Update

Once you’ve changed the runtime:

1. Run a test from the Lambda console.
2. Check your CloudWatch Logs for any import or dependency errors.

1. Reinstall dependencies using:
  pip install -r requirements.txt –target ./package
2. Redeploy your updated package if needed.

Handling Library Compatibility

If your function depends on external libraries, make sure they work with the new runtime.
You can test locally using:

python3.11 -m pip install -r requirements.txt

python3.11 my_script.py

If everything runs without issues, you’re good to deploy!

Keeping your AWS Lambda Python runtime up to date is one of the simplest but most important maintenance tasks.
It ensures:

- Security
- Speed
- Compatibility
- Stability

Pro Tip: Always stay one step ahead—upgrade to Python 3.11 today and future-proof your serverless applications