AWS Lambda Functions Skill

Develop high-performance serverless functions with best practices.

Quick Reference

Attribute	Value
AWS Service	Lambda
Complexity	Medium
Est. Time	5-15 min
Prerequisites	IAM Role, (Optional) VPC

Parameters

Required

Parameter	Type	Description	Validation
function_name	string	Function name	^[a-zA-Z0-9-_]{1,64}$
runtime	string	Runtime environment	python3.12, nodejs20.x, etc.
handler	string	Handler function	module.function
role_arn	string	Execution role ARN	Valid IAM role ARN

Optional

Parameter	Type	Default	Description
memory_mb	int	128	Memory allocation (128-10240)
timeout	int	3	Timeout seconds (1-900)
architecture	string	x86_64	x86_64 or arm64
environment	object	{}	Environment variables
vpc_config	object	null	VPC configuration

Execution Flow

1. Package code and dependencies
2. Create/update function
3. Configure triggers
4. Set concurrency limits
5. Test invocation
6. Monitor cold starts

Implementation

Create Function

# Create deployment package
zip -r function.zip . -x "*.git*"

# Create function
aws lambda create-function \
  --function-name my-function \
  --runtime python3.12 \
  --architectures arm64 \
  --handler main.handler \
  --role arn:aws:iam::123456789012:role/lambda-role \
  --zip-file fileb://function.zip \
  --memory-size 1024 \
  --timeout 30 \
  --environment "Variables={LOG_LEVEL=INFO}" \
  --tracing-config Mode=Active

Handler Template (Python)

import json
import logging

logger = logging.getLogger()
logger.setLevel(logging.INFO)

def handler(event, context):
    """
    Lambda handler function.

    Args:
        event: Trigger event data
        context: Runtime context (request_id, memory_limit, etc.)

    Returns:
        Response object or value
    """
    try:
        logger.info(f"Event: {json.dumps(event)}")

        # Business logic here
        result = process_event(event)

        return {
            "statusCode": 200,
            "body": json.dumps(result)
        }
    except Exception as e:
        logger.error(f"Error: {str(e)}")
        return {
            "statusCode": 500,
            "body": json.dumps({"error": str(e)})
        }

Handler Template (Node.js)

export const handler = async (event, context) => {
    console.log('Event:', JSON.stringify(event));

    try {
        const result = await processEvent(event);

        return {
            statusCode: 200,
            body: JSON.stringify(result)
        };
    } catch (error) {
        console.error('Error:', error);
        return {
            statusCode: 500,
            body: JSON.stringify({ error: error.message })
        };
    }
};

Memory/CPU Optimization

Memory	vCPU	Network	Use Case
128 MB	0.08	Low	Simple transforms
512 MB	0.33	Low	Basic API handlers
1024 MB	0.58	Medium	Standard workloads
1769 MB	1.0	Medium	CPU-bound tasks
3008 MB	2.0	High	Parallel processing
10240 MB	6.0	Very High	Data processing

Cold Start Mitigation

1. Use arm64: ~34% better price-performance
2. Minimize package: Only required dependencies
3. Use Layers: Shared dependencies
4. Provisioned Concurrency: Pre-warmed functions
5. SnapStart (Java): Cached initialization
6. Avoid VPC: Unless necessary (+1s cold start)

Troubleshooting

Common Issues

Symptom	Cause	Solution
Timeout	Long execution	Increase timeout, optimize code
OOM (signal: killed)	Memory exceeded	Increase memory
Import error	Missing dependency	Check package includes deps
Permission denied	IAM role	Update execution role

Debug Checklist

• Handler path correct (file.function)?
• All dependencies packaged?
• Execution role has permissions?
• Environment variables set?
• Memory sufficient for workload?
• Timeout appropriate?
• VPC has NAT for internet?

CloudWatch Log Patterns

Task timed out after X.XX seconds → Increase timeout
Runtime exited with error: signal: killed → Increase memory
Unable to import module → Check handler path/dependencies
ECONNREFUSED → Check VPC/security group

Test Template

def test_lambda_handler():
    # Arrange
    event = {"key": "value"}
    context = MockContext()

    # Act
    response = handler(event, context)

    # Assert
    assert response["statusCode"] == 200
    body = json.loads(response["body"])
    assert "result" in body

Observability

X-Ray Tracing

from aws_xray_sdk.core import xray_recorder

@xray_recorder.capture('process_data')
def process_data(data):
    # Traced function
    pass

Structured Logging

{
  "level": "INFO",
  "message": "Processing request",
  "request_id": "abc-123",
  "function_name": "my-function",
  "cold_start": true
}

Assets

• assets/lambda-template.py - Python handler template

References

• Lambda Developer Guide
• Lambda Best Practices