AWS Lambda

AWS Lambda runs code without provisioning servers. You pay only for compute time consumed. Lambda automatically scales from a few requests per day to thousands per second.

Core Concepts
Common Patterns
CLI Reference
Best Practices
Troubleshooting
References

Core Concepts

Function

Your code packaged with configuration. Includes runtime, handler, memory, timeout, and IAM role.

Invocation Types

Type	Description	Use Case
Synchronous	Caller waits for response	API Gateway, direct invoke
Asynchronous	Fire and forget	S3, SNS, EventBridge
Poll-based	Lambda polls source	SQS, Kinesis, DynamoDB Streams

Execution Environment

Lambda creates execution environments to run your function. Components:

Cold start: New environment initialization
Warm start: Reusing existing environment
Handler: Entry point function
Context: Runtime information

Layers

Reusable packages of libraries, dependencies, or custom runtimes (up to 5 per function).

Common Patterns

Create a Python Function

AWS CLI:

bash

# Create deployment package
zip function.zip lambda_function.py

# Create function
aws lambda create-function \
  --function-name MyFunction \
  --runtime python3.12 \
  --role arn:aws:iam::123456789012:role/lambda-role \
  --handler lambda_function.handler \
  --zip-file fileb://function.zip \
  --timeout 30 \
  --memory-size 256

# Update function code
aws lambda update-function-code \
  --function-name MyFunction \
  --zip-file fileb://function.zip

boto3:

python

import boto3
import zipfile
import io

lambda_client = boto3.client('lambda')

# Create zip in memory
zip_buffer = io.BytesIO()
with zipfile.ZipFile(zip_buffer, 'w') as zf:
    zf.writestr('lambda_function.py', '''
def handler(event, context):
    return {"statusCode": 200, "body": "Hello"}
''')
zip_buffer.seek(0)

# Create function
lambda_client.create_function(
    FunctionName='MyFunction',
    Runtime='python3.12',
    Role='arn:aws:iam::123456789012:role/lambda-role',
    Handler='lambda_function.handler',
    Code={'ZipFile': zip_buffer.read()},
    Timeout=30,
    MemorySize=256
)

Add S3 Trigger

bash

# Add permission for S3 to invoke Lambda
aws lambda add-permission \
  --function-name MyFunction \
  --statement-id s3-trigger \
  --action lambda:InvokeFunction \
  --principal s3.amazonaws.com \
  --source-arn arn:aws:s3:::my-bucket \
  --source-account 123456789012

# Configure S3 notification (see S3 skill)

Add SQS Event Source

bash

aws lambda create-event-source-mapping \
  --function-name MyFunction \
  --event-source-arn arn:aws:sqs:us-east-1:123456789012:my-queue \
  --batch-size 10 \
  --maximum-batching-window-in-seconds 5

Environment Variables

bash

aws lambda update-function-configuration \
  --function-name MyFunction \
  --environment "Variables={DB_HOST=mydb.cluster-xyz.us-east-1.rds.amazonaws.com,LOG_LEVEL=INFO}"

Create and Attach Layer

bash

# Create layer
zip -r layer.zip python/

aws lambda publish-layer-version \
  --layer-name my-dependencies \
  --compatible-runtimes python3.12 \
  --zip-file fileb://layer.zip

# Attach to function
aws lambda update-function-configuration \
  --function-name MyFunction \
  --layers arn:aws:lambda:us-east-1:123456789012:layer:my-dependencies:1

Invoke Function

bash

# Synchronous invoke
aws lambda invoke \
  --function-name MyFunction \
  --payload '{"key": "value"}' \
  response.json

# Asynchronous invoke
aws lambda invoke \
  --function-name MyFunction \
  --invocation-type Event \
  --payload '{"key": "value"}' \
  response.json

CLI Reference

Function Management

Command	Description
`aws lambda create-function`	Create new function
`aws lambda update-function-code`	Update function code
`aws lambda update-function-configuration`	Update settings
`aws lambda delete-function`	Delete function
`aws lambda list-functions`	List all functions
`aws lambda get-function`	Get function details

Invocation

Command	Description
`aws lambda invoke`	Invoke function
`aws lambda invoke-async`	Async invoke (deprecated)

Event Sources

Command	Description
`aws lambda create-event-source-mapping`	Add event source
`aws lambda list-event-source-mappings`	List mappings
`aws lambda update-event-source-mapping`	Update mapping
`aws lambda delete-event-source-mapping`	Remove mapping

Permissions

Command	Description
`aws lambda add-permission`	Add resource-based policy
`aws lambda remove-permission`	Remove permission
`aws lambda get-policy`	View resource policy

Best Practices

Performance

Right-size memory: More memory = more CPU = faster execution
Minimize cold starts: Keep functions warm, use Provisioned Concurrency
Optimize package size: Smaller packages deploy faster
Use layers for shared dependencies
Initialize outside handler: Reuse connections across invocations

python

# GOOD: Initialize outside handler
import boto3
dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('MyTable')

def handler(event, context):
    # Reuses existing connection
    return table.get_item(Key={'id': event['id']})

Security

Least privilege IAM roles — only grant needed permissions
Use Secrets Manager for sensitive data
Enable VPC only if needed (adds latency)
Encrypt environment variables with KMS

Cost Optimization

Set appropriate timeout — don't use max 15 minutes unnecessarily
Use ARM architecture (Graviton2) for 34% better price/performance
Batch process where possible
Use Reserved Concurrency to limit costs

Reliability

Configure DLQ for async invocations
Handle retries — async events retry twice
Make handlers idempotent
Use structured logging

Troubleshooting

Timeout Errors

Symptom:

Task timed out after X seconds

Causes:

Function takes longer than timeout
Network call to unreachable resource
VPC configuration issues

Debug:

bash

# Check function configuration
aws lambda get-function-configuration \
  --function-name MyFunction \
  --query "Timeout"

# Increase timeout
aws lambda update-function-configuration \
  --function-name MyFunction \
  --timeout 60

Out of Memory

Symptom: Function crashes with memory error

Fix:

bash

aws lambda update-function-configuration \
  --function-name MyFunction \
  --memory-size 512

Cold Start Latency

Causes:

Large deployment package
VPC configuration
Many dependencies to load

Solutions:

Use Provisioned Concurrency
Reduce package size
Use layers for dependencies
Consider Graviton2 (ARM)

bash

# Enable Provisioned Concurrency
aws lambda put-provisioned-concurrency-config \
  --function-name MyFunction \
  --qualifier LIVE \
  --provisioned-concurrent-executions 5

Permission Denied

Symptom:

AccessDeniedException

Debug:

bash

# Check execution role
aws lambda get-function-configuration \
  --function-name MyFunction \
  --query "Role"

# Check role policies
aws iam list-attached-role-policies \
  --role-name lambda-role

VPC Connectivity Issues

Symptom: Cannot reach internet or AWS services

Causes:

No NAT Gateway for internet access
Missing VPC endpoint for AWS services
Security group blocking outbound

Solutions:

Add NAT Gateway for internet
Add VPC endpoints for AWS services
Check security group rules

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SKILL.md Content

AWS Lambda

Table of Contents

Core Concepts

Function

Invocation Types

Execution Environment

Layers

Common Patterns

Create a Python Function

Add S3 Trigger

Add SQS Event Source

Environment Variables

Create and Attach Layer

Invoke Function

CLI Reference

Function Management

Invocation

Event Sources

Permissions

Best Practices

Performance

Security

Cost Optimization

Reliability

Troubleshooting

Timeout Errors

Out of Memory

Cold Start Latency

Permission Denied

VPC Connectivity Issues

References