REST API creation in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a REST API?

A REST API is a way for different software to talk to each other over the internet using simple commands like GET, POST, PUT, and DELETE.

beginner

What AWS service is commonly used to create REST APIs?

AWS API Gateway is used to create, publish, and manage REST APIs easily without managing servers.

beginner

What is an endpoint in a REST API?

An endpoint is a URL where the API listens for requests and sends back responses.

beginner

Why do we use HTTP methods like GET and POST in REST APIs?

HTTP methods tell the API what action to perform: GET to read data, POST to create data, PUT to update, and DELETE to remove data.

intermediate

How does AWS Lambda work with API Gateway in REST API creation?

API Gateway receives requests and triggers AWS Lambda functions to run code that processes the request and returns a response.

Which AWS service helps you create a REST API without managing servers?

A AWS API Gateway

B Amazon S3

C AWS EC2

D Amazon RDS

AWS API Gateway is designed to create and manage REST APIs without needing to manage servers.

What HTTP method is used to retrieve data from a REST API?

A GET

B POST

C DELETE

D PUT

GET is used to request and retrieve data from a REST API.

In AWS, which service runs your backend code when triggered by API Gateway?

A Amazon DynamoDB

B AWS Lambda

C Amazon S3

D AWS CloudWatch

AWS Lambda runs your code in response to API Gateway requests without managing servers.

What is an API endpoint?

A A database where API data is stored

B A security key for API access

C A URL where the API listens for requests

D A programming language for APIs

An endpoint is the URL where the API receives requests and sends responses.

Which HTTP method should you use to delete data via a REST API?

A PUT

B POST

C GET

D DELETE

DELETE is the HTTP method used to remove data through a REST API.

Explain how AWS API Gateway and AWS Lambda work together to create a REST API.

Think about the flow from client request to response.

Describe the main HTTP methods used in REST APIs and their purposes.

Focus on what each method does with data.

Practice

1. What is the main purpose of creating a REST API in AWS?

easy

A. To store large amounts of data securely in the cloud.

B. To allow different applications to communicate over the internet using defined paths and actions.

C. To run virtual machines for hosting websites.

D. To create user accounts and manage permissions.

Solution

1. Step 1: Understand REST API purpose

   REST APIs enable communication between apps using simple commands over the internet.

2. Step 2: Identify AWS REST API role

   In AWS, REST APIs define resources (paths) and methods (actions) to allow this communication.

3. Final Answer:

   To allow different applications to communicate over the internet using defined paths and actions. -> Option B

4. Quick Check:

   REST API = communication interface [OK]

Hint: REST APIs connect apps via internet paths and actions [OK]

Common Mistakes:

• Confusing REST API with data storage services
• Thinking REST API runs virtual machines
• Mixing REST API with user management

2. Which AWS service is primarily used to create REST APIs?

easy

A. Amazon API Gateway

B. AWS Lambda

C. Amazon S3

D. Amazon EC2

Solution

1. Step 1: Identify AWS services for APIs

   Amazon API Gateway is designed to create, publish, and manage REST APIs.

2. Step 2: Differentiate other services

   Amazon S3 stores files, Lambda runs code, EC2 runs servers, but API Gateway manages APIs.

3. Final Answer:

   Amazon API Gateway -> Option A

4. Quick Check:

   API Gateway = REST API service [OK]

Hint: API Gateway is the AWS REST API builder [OK]

Common Mistakes:

• Choosing Lambda as the API creator
• Confusing S3 with API service
• Selecting EC2 for API management

3. Given this API Gateway setup: a resource path /books with a GET method using MOCK integration. What happens when a client sends a GET request to /books?

medium

A. The API fetches book data from a connected database.

B. The API returns an error because MOCK integration is invalid.

C. The API triggers a Lambda function to process the request.

D. The API returns a predefined mock response without calling any backend.

Solution

1. Step 1: Understand MOCK integration

   MOCK integration returns a fixed response defined in API Gateway without backend calls.

2. Step 2: Analyze GET method on /books

   Since GET uses MOCK, the client receives the mock response directly.

3. Final Answer:

   The API returns a predefined mock response without calling any backend. -> Option D

4. Quick Check:

   MOCK integration = fixed response [OK]

Hint: MOCK returns fixed response, no backend called [OK]

Common Mistakes:

• Assuming MOCK calls database or Lambda
• Thinking MOCK integration causes errors
• Confusing MOCK with real backend integration

4. You created a POST method on resource /orders in API Gateway but get a 403 Forbidden error when testing. What is the most likely cause?

medium

A. The MOCK integration is missing a response template.

B. The resource path /orders is misspelled in the client request.

C. The method does not have permission to invoke the backend service.

D. The API Gateway does not support POST methods.

Solution

1. Step 1: Understand 403 Forbidden in API Gateway

   403 usually means permission denied to invoke backend or access resource.

2. Step 2: Check method permissions

   POST method likely lacks permission to call backend service, causing 403 error.

3. Final Answer:

   The method does not have permission to invoke the backend service. -> Option C

4. Quick Check:

   403 = permission denied [OK]

Hint: 403 means permission denied to backend [OK]

Common Mistakes:

• Assuming API Gateway disallows POST
• Blaming client path spelling without checking
• Thinking MOCK integration causes 403

5. You want to create a REST API with a resource /users that supports GET and POST methods. You start with MOCK integration for both methods to test. Later, you want GET to fetch data from a Lambda function and POST to store data in DynamoDB via Lambda. What is the best approach to achieve this?

hard

A. Create the API with MOCK integration first, then update GET and POST methods to use Lambda integration with proper permissions.

B. Create separate APIs for MOCK and Lambda integrations and switch clients between them.

C. Use MOCK integration permanently because it is simpler and faster.

D. Directly connect POST method to DynamoDB without Lambda and keep GET as MOCK.

Solution

1. Step 1: Start with MOCK integration for testing

   MOCK lets you test API behavior without backend, a good first step.

2. Step 2: Update methods to Lambda integration

   Later, replace MOCK with Lambda integration for GET and POST to connect real backend logic.

3. Step 3: Ensure permissions and backend setup

   Configure Lambda permissions and DynamoDB access properly for smooth operation.

4. Final Answer:

   Create the API with MOCK integration first, then update GET and POST methods to use Lambda integration with proper permissions. -> Option A

5. Quick Check:

   Start MOCK, then switch to Lambda integration [OK]

Hint: Test with MOCK, then switch methods to Lambda integration [OK]

Common Mistakes:

• Trying to use MOCK and Lambda in separate APIs
• Keeping MOCK integration permanently
• Connecting POST directly to DynamoDB without Lambda