AWS Lambda Functions Overview
AWS Lambda enables you to run code without provisioning or managing servers. Build serverless applications using event-driven triggers, pay only for compute time consumed, and scale automatically with workload.
When to Use API endpoints and webhooks Scheduled batch jobs and data processing Real-time file processing (S3 uploads) Event-driven workflows (SNS, SQS) Microservices and backend APIs Data transformations and ETL jobs IoT and sensor data processing WebSocket connections Implementation Examples 1. Basic Lambda Function with AWS CLI
Create Lambda execution role
aws iam create-role \ --role-name lambda-execution-role \ --assume-role-policy-document '{ "Version": "2012-10-17", "Statement": [{ "Effect": "Allow", "Principal": {"Service": "lambda.amazonaws.com"}, "Action": "sts:AssumeRole" }] }'
Attach basic execution policy
aws iam attach-role-policy \ --role-name lambda-execution-role \ --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
Create function from ZIP
zip function.zip index.js aws lambda create-function \ --function-name my-function \ --runtime nodejs18.x \ --role arn:aws:iam::ACCOUNT:role/lambda-execution-role \ --handler index.handler \ --zip-file fileb://function.zip \ --timeout 30 \ --memory-size 256 \ --environment Variables={ENV=production,DB_HOST=db.example.com}
Invoke function
aws lambda invoke \ --function-name my-function \ --payload '{"name":"John","age":30}' \ response.json
- Lambda Function with Node.js // index.js exports.handler = async (event) => { console.log('Event:', JSON.stringify(event));
try { // Parse different event sources const body = typeof event.body === 'string' ? JSON.parse(event.body) : event.body || {};
// Process S3 event
if (event.Records && event.Records[0].s3) {
const bucket = event.Records[0].s3.bucket.name;
const key = event.Records[0].s3.object.key;
console.log(`Processing S3 object: ${bucket}/${key}`);
}
// Database query simulation
const results = await queryDatabase(body);
return {
statusCode: 200,
headers: {
'Content-Type': 'application/json',
'Access-Control-Allow-Origin': '*'
},
body: JSON.stringify({
message: 'Success',
data: results
})
};
} catch (error) { console.error('Error:', error); return { statusCode: 500, body: JSON.stringify({ error: error.message }) }; } };
async function queryDatabase(params) { // Simulate database call return { items: [] }; }
- Terraform Lambda Deployment
main.tf
terraform { required_providers { aws = { source = "hashicorp/aws" version = "~> 5.0" } } }
provider "aws" { region = var.aws_region }
Lambda execution role
resource "aws_iam_role" "lambda_role" { name = "lambda-execution-role"
assume_role_policy = jsonencode({ Version = "2012-10-17" Statement = [{ Action = "sts:AssumeRole" Effect = "Allow" Principal = { Service = "lambda.amazonaws.com" } }] }) }
CloudWatch Logs policy
resource "aws_iam_role_policy_attachment" "lambda_logs" { role = aws_iam_role.lambda_role.name policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole" }
S3 Lambda Layer (dependencies)
resource "aws_lambda_layer_version" "dependencies" { filename = "layer.zip" layer_name = "nodejs-dependencies" compatible_runtimes = ["nodejs18.x"] }
Lambda function
resource "aws_lambda_function" "api_handler" { filename = "lambda.zip" function_name = "api-handler" role = aws_iam_role.lambda_role.arn handler = "index.handler" runtime = "nodejs18.x" timeout = 30 memory_size = 256
layers = [aws_lambda_layer_version.dependencies.arn]
environment { variables = { STAGE = "production" DB_HOST = var.database_host } }
depends_on = [aws_iam_role_policy_attachment.lambda_logs] }
API Gateway trigger
resource "aws_lambda_permission" "api_gateway" { statement_id = "AllowAPIGatewayInvoke" action = "lambda:InvokeFunction" function_name = aws_lambda_function.api_handler.function_name principal = "apigateway.amazonaws.com" }
S3 trigger
resource "aws_lambda_permission" "s3_trigger" { statement_id = "AllowS3Invoke" action = "lambda:InvokeFunction" function_name = aws_lambda_function.api_handler.function_name principal = "s3.amazonaws.com" source_arn = aws_s3_bucket.upload_bucket.arn }
resource "aws_s3_bucket_notification" "bucket_notification" { bucket = aws_s3_bucket.upload_bucket.id depends_on = [aws_lambda_permission.s3_trigger]
lambda_function { lambda_function_arn = aws_lambda_function.api_handler.arn events = ["s3:ObjectCreated:*"] filter_prefix = "uploads/" filter_suffix = ".jpg" } }
- Lambda with SAM (Serverless Application Model)
template.yaml
AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31
Globals: Function: Timeout: 30 MemorySize: 256 Runtime: nodejs18.x Tracing: Active
Parameters: Environment: Type: String Default: dev AllowedValues: [dev, prod]
Resources: # Lambda function MyFunction: Type: AWS::Serverless::Function Properties: FunctionName: !Sub '${Environment}-my-function' CodeUri: src/ Handler: index.handler Architectures: - x86_64 Environment: Variables: STAGE: !Ref Environment Policies: - DynamoDBCrudPolicy: TableName: !Ref DataTable - S3CrudPolicy: BucketName: !Ref DataBucket Events: ApiEvent: Type: Api Properties: Path: /api/{proxy+} Method: ANY RestApiId: !Ref MyApi S3Upload: Type: S3 Properties: Bucket: !Ref DataBucket Events: s3:ObjectCreated:* Filter: S3Key: Rules: - Name: prefix Value: uploads/
# DynamoDB table DataTable: Type: AWS::DynamoDB::Table Properties: TableName: !Sub '${Environment}-data' BillingMode: PAY_PER_REQUEST AttributeDefinitions: - AttributeName: id AttributeType: S KeySchema: - AttributeName: id KeyType: HASH
# S3 bucket DataBucket: Type: AWS::S3::Bucket Properties: BucketName: !Sub '${Environment}-data-${AWS::AccountId}' VersioningConfiguration: Status: Enabled
# API Gateway MyApi: Type: AWS::Serverless::Api Properties: Name: !Sub '${Environment}-api' StageName: !Ref Environment Cors: AllowMethods: "''" AllowHeaders: "'Content-Type,Authorization'" AllowOrigin: "''"
Outputs: FunctionArn: Value: !GetAtt MyFunction.Arn ApiEndpoint: Value: !Sub 'https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com'
- Lambda Layers for Code Sharing
Create layer directory structure
mkdir -p layer/nodejs/node_modules cd layer/nodejs
Install dependencies
npm install lodash axios moment
Go back and create zip
cd .. zip -r layer.zip .
Upload layer
aws lambda publish-layer-version \ --layer-name shared-utils \ --zip-file fileb://layer.zip \ --compatible-runtimes nodejs18.x
Best Practices ✅ DO Use environment variables for configuration Implement proper error handling and logging Optimize package size and dependencies Set appropriate timeout and memory Use Lambda Layers for shared code Implement concurrency limits Enable X-Ray tracing for debugging Use reserved concurrency for critical functions ❌ DON'T Store sensitive data in code Create long-running operations (>15 min) Ignore cold start optimization Forget to handle concurrent executions Ignore CloudWatch metrics Use too much memory unnecessarily Monitoring & Troubleshooting CloudWatch Logs for application logging CloudWatch Metrics for duration, errors, throttles X-Ray tracing for performance analysis Dead Letter Queues for failed messages Alarms for errors and throttling Resources AWS Lambda Developer Guide Lambda Best Practices AWS SAM Documentation