Creating modern, scalable web applications often requires backend APIs that handle create, read, update, and delete operations—collectively known as CRUD. In this tutorial, we’ll walk through building a fully serverless CRUD API on AWS, leveraging managed services so you never worry about provisioning or maintaining servers.

Our architecture relies on five core AWS services: API Gateway for routing, AWS Lambda for business logic, Amazon DynamoDB for data storage, CloudWatch for monitoring and logging, and IAM for secure permission management. Together they provide automatic scaling, cost efficiency, and simplified deployments.

High-Level Workflow

A client—such as a web browser or API testing tool—sends an HTTP request to API Gateway. Gateway invokes the matching Lambda function, passing through all headers and payload details. That function performs the requested CRUD operation on a DynamoDB table and writes execution logs to CloudWatch. IAM roles ensure that Lambda has exactly the permissions it needs. Finally, the function’s response returns through API Gateway to the client.

Step 1: Create the DynamoDB Table

In the AWS Console, navigate to DynamoDB and create a table named tasks with a partition key called ID. DynamoDB is schema-less—only the partition key is required—letting you store arbitrary attributes per item as your application evolves.

Step 2: Set Up the Lambda Function

Head to AWS Lambda and create a function named taskCrudHandler, choosing Node.js (or Python) as the runtime. Opt to “Create a new role with basic Lambda permissions” so logs flow into CloudWatch automatically. Then, open the function’s Permissions tab, click the linked IAM role, and attach both the AmazonDynamoDBFullAccess and CloudWatchLogsFullAccess policies—granting DynamoDB and logging access.

Step 3: Write and Deploy Your Code

In the Lambda editor, paste your CRUD handlers: a GET handler to scan the tasks table, POST to insert new records, PATCH to update existing items, and DELETE to remove entries by ID. Each uses the AWS SDK’s DynamoDB DocumentClient. Click “Deploy” to publish your updated function.

Step 4: Configure API Gateway

In API Gateway, create a REST API named taskAPI. Add a resource at /task and enable CORS for browser clients. Under that resource, define GET, POST, PATCH, and DELETE methods. For each, enable Lambda Proxy Integration and choose taskCrudHandler. Finally, deploy to a stage called “production,” which gives you an invoke URL to use in your frontend or API client.

Step 5: Test with Postman

Use Postman (or curl) to exercise each endpoint: a GET returns an empty array at first, POST adds new tasks, GET then shows those tasks, PATCH updates item attributes, and DELETE removes them by ID. Verify data changes directly in the DynamoDB Console and inspect HTTP responses for confirmation.

Step 6: Debug via CloudWatch

To see CloudWatch in action, introduce a deliberate bug in your Lambda code. When you invoke it, API Gateway will surface a 500 Internal Server Error. In the AWS Console, open CloudWatch’s Log Groups, find the taskCrudHandler group, and inspect the latest log stream. You’ll see the full error stack—such as “Cannot access variable before initialization”—allowing you to pinpoint and fix issues immediately.

Conclusion

By combining API Gateway, Lambda, DynamoDB, IAM, and CloudWatch, you can build a complete serverless CRUD API on AWS. This architecture removes server management overhead, scales automatically, and keeps costs low—perfect for modern web, mobile, or IoT backends. Start with this pattern, then extend it with authentication, caching, or other AWS services as your application grows.