Tips and Tricks #211: Use AWS Lambda Layers for Shared Dependencies

Share common code and dependencies across Lambda functions to reduce deployment size.

Code Snippet

# serverless.yml
service: my-service

provider:
  name: aws
  runtime: python3.11

layers:
  commonDeps:
    path: layers/common
    description: Shared dependencies
    compatibleRuntimes:
      - python3.11

functions:
  userHandler:
    handler: handlers/user.handler
    layers:
      - !Ref CommonDepsLambdaLayer
  
  orderHandler:
    handler: handlers/order.handler
    layers:
      - !Ref CommonDepsLambdaLayer

# layers/common/python/requirements.txt
# boto3, requests, etc.

Why This Helps

• Reduces deployment package size by 80%+
• Faster cold starts
• Centralized dependency management

How to Test

• Deploy and verify functions work
• Check deployment package sizes

When to Use

Multiple Lambda functions sharing common libraries or utilities.

Performance/Security Notes

Layer updates require redeploying functions. Keep layers under 50MB unzipped.

References

• https://docs.aws.amazon.com/lambda/latest/dg/chapter-layers.html

Try this tip in your next project and share your results in the comments!