Serverless CRUD REST API with AWS Lambda and RDS (PostgreSQL)

Project Overview

This project implements a serverless CRUD (Create, Read, Update, Delete) REST API using Node.js, AWS Lambda, Amazon API Gateway, and Amazon RDS PostgreSQL. The API allows users to perform CRUD operations on a users table in PostgreSQL. All requests are routed through API Gateway to a single AWS Lambda function, which interacts with the RDS database inside a VPC for secure access. CloudWatch logs monitor Lambda executions.

Flow:

1. Client (Postman / Browser / App) sends HTTP request.
2. API Gateway receives the request and triggers Lambda.
3. Lambda executes CRUD logic and connects to PostgreSQL (inside VPC).
4. Database returns the result to Lambda.
5. Lambda sends response back to API Gateway.
6. API Gateway returns JSON response to the client.

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Features

• Create User → Insert new record into the database
• Read All Users → Fetch all users
• Read User by ID → Fetch a single user by ID
• Update User → Modify existing user
• Delete User → Remove a user by ID

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Technology Stack

• Node.js (JavaScript)
• AWS Lambda (single file for all CRUD operations)
• Amazon RDS PostgreSQL
• API Gateway (REST API, Regional, TLS 1.3)
• AWS VPC and Security Groups
• AWS CloudWatch Logs

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API Endpoints

Method	Endpoint	Description
POST	/users	Create a new user
GET	/users	Get all users
GET	/users/{id}	Get a user by ID
PUT	/users/{id}	Update a user by ID
DELETE	/users/{id}	Delete a user by ID

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Environment Variables

The Lambda function requires the following environment variables:

Variable	Description
DB_HOST	RDS endpoint (hostname)
DB_USER	Database username
DB_PASSWORD	Database password
DB_NAME	Database name

Security Tip: Never hardcode credentials in your code. Use environment variables or AWS Secrets Manager.

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Database Table

SQL to create the users table:

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(50) NOT NULL
);

Setup Instructions

1. AWS Infrastructure

1. Create a VPC with private subnets for Lambda and RDS.
2. Create Security Groups:
   • RDS-SG: Allow inbound PostgreSQL (port 5432) from Lambda-SG.
   • Lambda-SG: Allow outbound traffic to RDS.
3. Launch Amazon RDS PostgreSQL in private subnets.
4. Enable CloudWatch Logging for Lambda.

2. Deploy Lambda Function

1. Upload index.js (single file with all CRUD logic) to Lambda.
2. Add environment variables: DB_HOST, DB_USER, DB_PASSWORD, DB_NAME.
3. Attach Lambda to the VPC and select the correct subnets and security group.
4. Assign IAM role with Lambda execution permissions.

Note: The Lambda file contains all CRUD logic. The handler routes requests based on HTTP method and path.

3. Configure API Gateway

1. Create a REST API (Regional, TLS 1.3).
2. Add resources and methods:
   • /users → GET, POST
   • /users/{id} → GET, PUT, DELETE
3. Enable Lambda Proxy Integration for all methods.
4. Deploy API to a stage (e.g., dev) to generate the Invoke URL.

4. Test API Endpoints

Use Postman or curl for testing:

Create User (POST /users)

POST https://<invoke-url>/users
Content-Type: application/json

{
  "name": "Rabia",
  "email": "rabia@example.com"
}

Create User (POST /users)

POST https://<invoke-url>/users
Body:
{
  "name": "Rabia",
  "email": "rabia@example.com"
}

Get All Users (GET /users)

GET https://<invoke-url>/users

Get User by ID (GET /users/1)

GET https://<invoke-url>/users/1

Update User (PUT /users/1)

PUT https://<invoke-url>/users/1
Body:
{
  "name": "Rabia Updated",
  "email": "rabia.new@example.com"
}

Delete User (DELETE /users/1)

DELETE https://<invoke-url>/users/1

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Testing & Logging

Use Postman or curl to test each endpoint. All Lambda executions are logged in CloudWatch, including request method, body, SQL queries, and errors.