Lambda cold starts impact performance. After optimizing production Lambdas, here are strategies that work.

What are Cold Starts?

Cold starts occur when:

  • First invocation - New execution environment
  • Idle timeout - Environment recycled
  • Concurrency limit - New container needed

Optimization Strategies

Provisioned Concurrency

// CloudFormation
const function = new lambda.Function(this, 'MyFunction', {
    // ... configuration
});

new lambda.ProvisionedConcurrencyConfig(this, 'Provisioned', {
    function: function,
    qualifier: 'live',
    provisionedConcurrentExecutions: 10
});

SnapStart (Java)

# Enable SnapStart
Resources:
  MyFunction:
    Type: AWS::Lambda::Function
    Properties:
      SnapStart:
        ApplyOn: PublishedVersions

Initialization Optimization

// Bad: Heavy initialization in handler
exports.handler = async (event) => {
    const db = await connectDatabase(); // Cold start penalty
    const cache = await initializeCache(); // Cold start penalty
    // ...
};

// Good: Initialize outside handler
const db = await connectDatabase();
const cache = await initializeCache();

exports.handler = async (event) => {
    // Use pre-initialized resources
    return await processEvent(event, db, cache);
};

Best Practices

  1. Minimize dependencies - Smaller packages
  2. Use layers - Share code
  3. Optimize imports - Lazy loading
  4. Provisioned concurrency - For critical paths
  5. SnapStart - For Java functions
  6. Monitor - Track cold start frequency
  7. Warm functions - Keep-alive pings
  8. Right-sizing - Appropriate memory

Conclusion

Lambda cold start optimization requires:

  • Provisioned concurrency
  • Initialization optimization
  • Dependency minimization
  • Monitoring

Combine strategies for best results. The techniques shown here reduce cold start latency significantly.

AWS Lambda cold start optimization from February 2023, covering provisioned concurrency and initialization strategies.