AWS SAM Setup for Serverless Backend

AWS SAM Setup for Serverless Backend

AWS SAM (Serverless Application Model) is the official AWS tool for defining serverless resources. It extends CloudFormation with simplified syntax: instead of 50 lines of CloudFormation for Lambda + API Gateway + IAM, write 10 lines of SAM. Output is a full CloudFormation stack, versioned and rollbackable.

Unlike Serverless Framework, SAM is AWS-native with no abstraction over other providers. This is its advantage: full CloudFormation compatibility, native CDK integration, direct SAM CLI for local testing with real service mocks.

Installation and First Project

# macOS
brew tap aws/tap
brew install aws-sam-cli

# Linux
pip install aws-sam-cli

sam --version

sam init --runtime nodejs20.x --dependency-manager npm --app-template hello-world --name my-backend

Project Structure

my-backend/
├── template.yaml
├── samconfig.toml
├── src/
│   ├── handlers/
│   │   ├── api.ts
│   │   └── auth.ts
│   └── shared/
├── events/
└── __tests__/

template.yaml Configuration

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Globals:
  Function:
    Runtime: nodejs20.x
    Architectures: [arm64]
    MemorySize: 512
    Timeout: 10
    Environment:
      Variables:
        NODE_ENV: !Ref Stage

Parameters:
  Stage:
    Type: String
    Default: dev
    AllowedValues: [dev, staging, prod]

Resources:
  ApiGateway:
    Type: AWS::Serverless::HttpApi
    Properties:
      StageName: !Ref Stage

  ApiFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: src/handlers/api.handler
      Events:
        AnyRoute:
          Type: HttpApi
          Properties:
            ApiId: !Ref ApiGateway
            Method: ANY
            Path: /api/{proxy+}
      Policies:
        - DynamoDBCrudPolicy:
            TableName: !Ref MainTable
    Metadata:
      BuildMethod: esbuild
      BuildProperties:
        Minify: true
        Target: es2022

  MainTable:
    Type: AWS::DynamoDB::Table
    Properties:
      BillingMode: PAY_PER_REQUEST
      AttributeDefinitions:
        - { AttributeName: pk, AttributeType: S }
        - { AttributeName: sk, AttributeType: S }
      KeySchema:
        - { AttributeName: pk, KeyType: HASH }
        - { AttributeName: sk, KeyType: RANGE }

Outputs:
  ApiUrl:
    Value: !Sub 'https://${ApiGateway}.execute-api.${AWS::Region}.amazonaws.com/${Stage}'
  TableName:
    Value: !Ref MainTable

Handler

// src/handlers/api.ts
import type { APIGatewayProxyEventV2, APIGatewayProxyResultV2 } from 'aws-lambda';

export const handler = async (event: APIGatewayProxyEventV2): Promise<APIGatewayProxyResultV2> => {
  return {
    statusCode: 200,
    body: JSON.stringify({ message: 'Hello from SAM!' }),
  };
};

samconfig.toml

[default.deploy.parameters]
stack_name = "my-backend-dev"
s3_bucket = "sam-artifacts-eu-west-1"
region = "eu-west-1"
parameter_overrides = "Stage=dev"

[prod.deploy.parameters]
stack_name = "my-backend-prod"
s3_bucket = "sam-artifacts-eu-west-1"
region = "eu-west-1"
parameter_overrides = "Stage=prod"

Local Development

sam build

sam local start-api --env-vars env.json --port 3001

sam local invoke ApiFunction --event events/api-get.json

sam logs --stack-name my-backend-dev --tail

Deployment

sam deploy --guided

sam build && sam deploy

sam build && sam deploy --config-env prod

Timeframe

Basic SAM backend with Lambda + HTTP API + DynamoDB — 1–2 days. Full structure with authorizer, SQS, S3, and multi-environment config — 4–5 days.