🚀 Going Serverless: Deploying a Restaurant Booking API with Lambda and API Gateway

After building scalable infrastructure using EC2, Terraform, and Secrets Manager, it’s time to go fully serverless. In this post, we’ll migrate your app to use:

• 🧠 AWS Lambda — run code without managing servers
• 🌐 API Gateway — expose HTTPS endpoints
• 🔐 Secrets Manager — keep secrets out of your code
• 🗃️ DynamoDB or RDS Proxy — handle your database layer

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📦 Architecture Overview

Client → API Gateway → Lambda Functions → DB (DynamoDB or RDS via Proxy)
                                   ↓
                             Secrets Manager

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✅ Benefits of This Serverless Stack

Feature	Benefit
No server to manage	Pay-per-use compute
Autoscaling	Lambda scales on demand
Secure secrets	AWS Secrets Manager or Parameter Store
Low ops overhead	No patching, no EC2, no autoscaling setup
Fast deployment	Single command using CDK or SAM

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🔧 Step-by-Step: Deploy with AWS SAM (Serverless Application Model)

1. 🛠 Install SAM CLI

brew install aws/tap/aws-sam-cli
sam --version

2. 📁 Project Structure

restaurant-booking-api/
├── template.yaml        # SAM template (Infra as code)
├── app/
│   ├── __init__.py
│   └── handler.py       # Lambda function code
├── events/              # Example test events
└── requirements.txt

3. ✍️ Sample SAM Template (template.yaml)

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  BookingAPI:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.handler.lambda_handler
      Runtime: python3.11
      MemorySize: 512
      Timeout: 10
      Environment:
        Variables:
          DB_SECRET: /myapp/db-creds
      Events:
        ApiEvent:
          Type: Api
          Properties:
            Path: /bookings
            Method: post

4. 🧠 handler.py (Lambda Code)

import json, boto3, os

def lambda_handler(event, context):
    secrets = boto3.client('secretsmanager')
    response = secrets.get_secret_value(SecretId=os.environ['DB_SECRET'])
    creds = json.loads(response['SecretString'])

    booking = json.loads(event['body'])
    # Connect to DB, store booking using creds
    return {
        "statusCode": 200,
        "body": json.dumps({"message": "Booking successful"})
    }

5. 🚀 Deploy to AWS

sam build
sam deploy --guided

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🔐 Storing DB Credentials in Secrets Manager

aws secretsmanager create-secret \
  --name /myapp/db-creds \
  --secret-string '{"username":"admin","password":"mypassword"}'

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📊 Monitoring with CloudWatch

Each Lambda execution gets its own logs under /aws/lambda/. You can:

• Set up CloudWatch alarms for failure rates or latency
• Enable X-Ray tracing for distributed tracing

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🌍 Bonus: Custom Domain with API Gateway + ACM

aws acm request-certificate \
  --domain-name api.mkcloudai.com \
  --validation-method DNS

# Then link ACM to API Gateway via custom domain mappings.

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