API Gateway to DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the role of an API Gateway in a system that uses DynamoDB?

An API Gateway acts as a front door for clients to access backend services like DynamoDB. It handles request routing, authentication, and throttling, simplifying client interactions with the database.

intermediate

How does API Gateway improve scalability when accessing DynamoDB?

API Gateway manages traffic by throttling and caching requests, which prevents overload on DynamoDB. It also supports scaling by distributing requests efficiently and enabling serverless backend integration.

intermediate

What is a common pattern to securely connect API Gateway to DynamoDB?

Use AWS IAM roles and policies to grant API Gateway permission to access DynamoDB. This ensures secure, controlled access without exposing database credentials to clients.

beginner

Explain the request flow from a client to DynamoDB through API Gateway.

Client sends HTTP request → API Gateway receives and authenticates → API Gateway transforms request if needed → API Gateway calls DynamoDB using AWS SDK or service integration → DynamoDB processes and returns data → API Gateway sends response back to client.

intermediate

Why is caching important in API Gateway when working with DynamoDB?

Caching reduces the number of direct calls to DynamoDB by storing frequent responses temporarily. This lowers latency for clients and reduces cost and load on the database.

What does API Gateway primarily do when connected to DynamoDB?

A Runs complex queries on data

B Stores data permanently

C Replaces DynamoDB as a database

D Routes and manages client requests to DynamoDB

API Gateway routes and manages client requests but does not store data or replace the database.

Which AWS feature helps secure API Gateway's access to DynamoDB?

A IAM roles and policies

B CloudFront distributions

C S3 buckets

D EC2 instances

IAM roles and policies control permissions securely between API Gateway and DynamoDB.

How does caching in API Gateway affect DynamoDB usage?

A Increases the number of requests to DynamoDB

B Reduces latency and request load on DynamoDB

C Deletes data from DynamoDB

D Encrypts data in DynamoDB

Caching reduces latency and the number of requests sent to DynamoDB.

What is the first step when a client sends a request through API Gateway to DynamoDB?

A Data is cached

B DynamoDB processes the request

C API Gateway authenticates the request

D Request is stored in S3

API Gateway first authenticates the client request before forwarding it.

Which of the following is NOT a function of API Gateway in this architecture?

A Direct data storage

B Authentication

C Request throttling

D Request transformation

API Gateway does not store data directly; DynamoDB handles data storage.

Describe the end-to-end flow of a client request from API Gateway to DynamoDB and back.

Think about each step the request passes through and what each component does.

Explain how security is maintained when API Gateway accesses DynamoDB.

Focus on AWS security best practices for service-to-service communication.

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