AWS Lambda and API Gateway Integration Guide

Introduction

Serverless architecture has revolutionized how we build and deploy applications. AWS Lambda combined with API Gateway offers a powerful solution for creating scalable, maintenance-free APIs.

Architecture Overview

1. API Gateway Configuration

openapi: 3.0.0
info:
  title: Order Processing API
  version: 1.0.0
paths:
  /orders:
    post:
      summary: Create new order
      x-amazon-apigateway-integration:
        uri: arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/${OrderProcessorFunction}/invocations
        passthroughBehavior: when_no_match
        httpMethod: POST
        type: aws_proxy

2. Lambda Function Implementation

import { APIGatewayProxyHandler } from 'aws-lambda';
import { DynamoDB } from 'aws-sdk';

export const handler: APIGatewayProxyHandler = async (event) => {
  const dynamodb = new DynamoDB.DocumentClient();
  
  try {
    const order = JSON.parse(event.body || '{}');
    
    await dynamodb.put({
      TableName: 'Orders',
      Item: {
        orderId: uuid(),
        ...order,
        createdAt: new Date().toISOString()
      }
    }).promise();
    
    return {
      statusCode: 201,
      body: JSON.stringify({ message: 'Order created successfully' })
    };
  } catch (error) {
    return {
      statusCode: 500,
      body: JSON.stringify({ error: 'Internal server error' })
    };
  }
};

Best Practices

1. Error Handling

const errorHandler = (error: Error) => {
  if (error instanceof ValidationError) {
    return {
      statusCode: 400,
      body: JSON.stringify({
        error: 'Validation Error',
        details: error.details
      })
    };
  }
  
  console.error('Unexpected error:', error);
  return {
    statusCode: 500,
    body: JSON.stringify({
      error: 'Internal Server Error'
    })
  };
};

2. Input Validation

import * as Joi from 'joi';

const orderSchema = Joi.object({
  customerId: Joi.string().required(),
  items: Joi.array().items(
    Joi.object({
      productId: Joi.string().required(),
      quantity: Joi.number().min(1).required()
    })
  ).min(1).required()
});

Performance Optimization

1. Connection Reuse: Maintain persistent connections
2. Cold Start Mitigation: Use Provisioned Concurrency
3. Efficient Data Access: Implement DynamoDB DAX

// Connection reuse example
const dynamodb = new DynamoDB.DocumentClient();
let cachedConnection;

export const handler: APIGatewayProxyHandler = async (event) => {
  if (!cachedConnection) {
    cachedConnection = await createConnection();
  }
  // Use cached connection
};

Security Implementation

1. API Key Authentication

securitySchemes:
  api_key:
    type: apiKey
    name: x-api-key
    in: header

2. IAM Roles and Policies

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "dynamodb:PutItem",
        "dynamodb:GetItem",
        "dynamodb:Query"
      ],
      "Resource": "arn:aws:dynamodb:*:*:table/Orders"
    }
  ]
}

Monitoring and Logging

1. CloudWatch Metrics: Track invocation metrics
2. X-Ray Tracing: Implement distributed tracing
3. Structured Logging: Use standard log formats

const logger = {
  info: (message: string, context: object) => {
    console.log(JSON.stringify({
      level: 'INFO',
      message,
      timestamp: new Date().toISOString(),
      ...context
    }));
  }
};

Deployment Strategy

1. Infrastructure as Code: Use AWS CDK or CloudFormation
2. Stage Management: Implement multiple environments
3. Version Control: API versioning best practices

Conclusion

AWS Lambda and API Gateway provide a powerful combination for building serverless APIs. Following these best practices ensures a robust, scalable, and maintainable solution for enterprise applications.