API Gateway to DynamoDB

Introduction

An API Gateway acts as a front door to securely connect users to backend services like DynamoDB. It helps manage requests, control access, and simplify communication.

When you want to expose DynamoDB data securely to web or mobile apps.

When you need to control and monitor access to your database.

When you want to transform or validate requests before they reach DynamoDB.

When you want to handle multiple clients with a single entry point.

When you want to add caching or throttling to reduce load on DynamoDB.

Syntax

DynamoDB

API Gateway -> Integration Request -> DynamoDB Action -> Integration Response -> API Gateway Response

API Gateway acts as a proxy or direct integration to DynamoDB actions like GetItem, PutItem, Query.

You configure mapping templates to translate API requests into DynamoDB requests and responses back.

Examples

Fetch an item by its ID from DynamoDB through API Gateway.

DynamoDB

GET /items/{id} -> API Gateway -> DynamoDB GetItem

Add a new item to DynamoDB using API Gateway POST request.

DynamoDB

POST /items -> API Gateway -> DynamoDB PutItem

Query items by category using API Gateway and DynamoDB Query operation.

DynamoDB

GET /items?category=books -> API Gateway -> DynamoDB Query

Sample Program

This flow shows how API Gateway acts as a bridge between a client and DynamoDB. It securely handles the request, translates it, and returns the data.

DynamoDB

1. Client sends GET request to API Gateway endpoint /items/{id}
2. API Gateway receives request and extracts {id} path parameter
3. API Gateway maps request to DynamoDB GetItem action with Key = {"id": {id}}
4. DynamoDB returns item data to API Gateway
5. API Gateway maps DynamoDB response to HTTP response
6. Client receives item data in JSON format

Important Notes

Always enable authorization (like IAM or Cognito) on API Gateway to protect your DynamoDB data.

Use request and response mapping templates to format data correctly between API Gateway and DynamoDB.

Consider enabling caching on API Gateway to reduce repeated DynamoDB calls and improve performance.

Summary

API Gateway provides a secure and manageable way to access DynamoDB.

It translates HTTP requests into DynamoDB actions and formats responses back to clients.

Use it to control access, monitor usage, and improve scalability of your database access.

Practice

1. What is the primary role of API Gateway when used with DynamoDB?

easy

A. To replace DynamoDB as a database

B. To store data directly in DynamoDB

C. To securely expose DynamoDB operations over HTTP

D. To perform complex data analytics on DynamoDB data

Solution

1. Step 1: Understand API Gateway's function

   API Gateway acts as a secure interface that translates HTTP requests into backend service calls.

2. Step 2: Identify its role with DynamoDB

   It exposes DynamoDB operations securely over HTTP, enabling controlled access and monitoring.

3. Final Answer:

   To securely expose DynamoDB operations over HTTP -> Option C

4. Quick Check:

   API Gateway = Secure HTTP access to DynamoDB [OK]

Hint: API Gateway acts as a secure HTTP front for DynamoDB [OK]

Common Mistakes:

• Thinking API Gateway stores data
• Confusing API Gateway with DynamoDB itself
• Assuming API Gateway performs data analytics

2. Which of the following is the correct way to define a GET method in API Gateway to fetch an item from DynamoDB?

easy

A. Use HTTP GET with a path parameter for the key and integrate with DynamoDB GetItem action

B. Use HTTP POST with a JSON body containing the key and integrate with DynamoDB PutItem action

C. Use HTTP DELETE with query parameters and integrate with DynamoDB DeleteItem action

D. Use HTTP PUT with path parameters and integrate with DynamoDB UpdateItem action

Solution

1. Step 1: Match HTTP method to DynamoDB action

   GET method is used to retrieve data, so it should map to DynamoDB's GetItem action.

2. Step 2: Use path parameter for key

   The key identifying the item is passed as a path parameter in the GET request.

3. Final Answer:

   Use HTTP GET with a path parameter for the key and integrate with DynamoDB GetItem action -> Option A

4. Quick Check:

   GET + path key = GetItem [OK]

Hint: GET method fetches data; use path parameter for key [OK]

Common Mistakes:

• Using POST instead of GET for fetching
• Confusing PutItem with GetItem
• Using wrong HTTP methods for actions

3. Given this API Gateway integration request mapping template snippet:

{
  "TableName": "Users",
  "Key": {
    "UserId": { "S": "$input.params('userId')" }
  }
}

What DynamoDB operation does this template prepare for?

medium

A. PutItem to insert a new user

B. GetItem to fetch a user by UserId

C. DeleteItem to remove a user

D. UpdateItem to modify user attributes

Solution

1. Step 1: Analyze the template structure

   The template specifies a TableName and a Key with UserId, which matches the input for a GetItem request.

2. Step 2: Match to DynamoDB operation

   GetItem requires TableName and Key to fetch an item; PutItem or UpdateItem would include Item or UpdateExpression fields.

3. Final Answer:

   GetItem to fetch a user by UserId -> Option B

4. Quick Check:

   TableName + Key = GetItem [OK]

Hint: TableName + Key in template means GetItem [OK]

Common Mistakes:

• Confusing GetItem with PutItem
• Assuming DeleteItem without DeleteExpression
• Ignoring the Key field meaning

4. You configured API Gateway to integrate with DynamoDB PutItem but receive a 400 Bad Request error. Which of these is the most likely cause?

medium

A. Missing required 'Item' field in the request mapping template

B. Using HTTP GET method instead of POST

C. Incorrect table name in the DynamoDB action

D. Not enabling CORS on API Gateway

Solution

1. Step 1: Understand PutItem requirements

   PutItem requires an 'Item' field specifying the data to insert; missing it causes a bad request.

2. Step 2: Evaluate other options

   Using GET instead of POST may cause issues but usually not 400 if mapping is correct; wrong table name causes 500 errors; CORS issues cause client-side errors, not 400 from API Gateway.

3. Final Answer:

   Missing required 'Item' field in the request mapping template -> Option A

4. Quick Check:

   PutItem needs 'Item' field [OK]

Hint: PutItem must include 'Item' in request template [OK]

Common Mistakes:

• Confusing HTTP method errors with mapping errors
• Ignoring required fields in request templates
• Assuming CORS causes 400 errors

5. You want to design a scalable API Gateway to DynamoDB system that supports thousands of requests per second with minimal latency. Which combination of design choices is best?

hard

A. Use API Gateway without caching, DynamoDB with provisioned capacity, and open access without authentication

B. Use API Gateway with caching disabled, DynamoDB with manual scaling, and no monitoring enabled

C. Use API Gateway with throttling disabled, DynamoDB with global tables disabled, and API keys for access control

D. Use API Gateway with caching enabled, DynamoDB with on-demand capacity mode, and IAM roles for secure access

Solution

1. Step 1: Choose scalable DynamoDB capacity mode

   On-demand capacity mode automatically scales to handle high request volumes without manual intervention.

2. Step 2: Enable API Gateway caching and secure access

   Caching reduces latency and load on DynamoDB; IAM roles provide secure, managed access.

3. Step 3: Avoid options that disable throttling or monitoring

   Disabling throttling or monitoring risks overload and lack of visibility; open access is insecure.

4. Final Answer:

   Use API Gateway with caching enabled, DynamoDB with on-demand capacity mode, and IAM roles for secure access -> Option D

5. Quick Check:

   Caching + on-demand + IAM = scalable & secure [OK]

Hint: Enable caching and on-demand capacity for scalability [OK]

Common Mistakes:

• Disabling throttling causing overload
• Using provisioned capacity without scaling
• Ignoring security best practices