REST API creation in AWS - Step-by-Step Execution

Process Flow - REST API creation

Define API Gateway REST API

↓

Create Resources (paths)

↓

Define Methods (GET, POST, etc.)

↓

Integrate Methods with Backend (Lambda, HTTP)

↓

Deploy API to Stage

↓

API is Ready to Receive Requests

This flow shows the steps to create a REST API using AWS API Gateway: define the API, add paths, set methods, connect to backend, deploy, then use.

Execution Sample

AWS

aws apigateway create-rest-api --name MyAPI
aws apigateway create-resource --rest-api-id <id> --parent-id <root> --path-part users
aws apigateway put-method --rest-api-id <id> --resource-id <users> --http-method GET --authorization-type NONE
aws apigateway put-integration --rest-api-id <id> --resource-id <users> --http-method GET --type MOCK
aws apigateway create-deployment --rest-api-id <id> --stage-name prod

This sequence creates a REST API named MyAPI with a /users GET method using a mock integration, then deploys it to the prod stage.

Process Table

Step	Action	Input	Result	Notes
1	Create REST API	Name=MyAPI	API ID=abc123	API created with unique ID
2	Create Resource	rest-api-id=abc123, path-part=users	Resource ID=res456	Resource /users added under root
3	Put Method	rest-api-id=abc123, resource-id=res456, method=GET	Method GET created	GET method added to /users
4	Put Integration	rest-api-id=abc123, resource-id=res456, method=GET, type=MOCK	Integration set	GET method linked to mock backend
5	Create Deployment	rest-api-id=abc123, stage=prod	Deployment ID=dep789	API deployed to prod stage
6	Test API	Invoke GET https://abc123.execute-api.region.amazonaws.com/prod/users	Response 200 OK	API responds as expected
7	Exit	N/A	End	API creation and deployment complete

💡 API is deployed and ready to receive requests at the prod stage

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
API ID	None	abc123	abc123	abc123	abc123	abc123	abc123
Resource ID	None	None	res456	res456	res456	res456	res456
Method GET	None	None	None	Created	Created	Created	Created
Integration	None	None	None	None	Set to MOCK	Set to MOCK	Set to MOCK
Deployment	None	None	None	None	None	dep789	dep789

Key Moments - 3 Insights

Why do we need to create a resource before adding a method?

Because methods like GET or POST belong to specific paths (resources). Step 2 creates the /users path, then step 3 adds GET to it.

What does the integration step do?

It connects the method to a backend service. In step 4, the GET method is linked to a MOCK integration, meaning it returns a fixed response.

Why is deployment necessary after creating methods and integrations?

Deployment (step 5) publishes the API configuration to a stage so it becomes accessible. Without deployment, the API changes are not live.

Visual Quiz - 3 Questions

Look at the execution table, what is the Resource ID after step 2?

A abc123

B res456

C dep789

D None

💡 Hint

Check the 'Result' column in row for step 2 in the execution_table.

At which step is the GET method created?

A Step 1

B Step 4

C Step 3

D Step 5

💡 Hint

Look for 'Method GET created' in the execution_table rows.

If we skip the deployment step, what happens when we try to call the API?

A API returns an error or is not reachable

B API responds with 200 OK

C API returns a mock response

D API automatically deploys

💡 Hint

Refer to the exit_note and step 5 about deployment necessity.

Concept Snapshot

AWS REST API creation steps:
1. Create API Gateway REST API
2. Add resources (paths)
3. Define methods (GET, POST)
4. Integrate methods with backend (Lambda, MOCK)
5. Deploy API to a stage
6. Use the deployed API endpoint
Deployment is required to make API live.

Full Transcript

To create a REST API in AWS, first define the API Gateway REST API. Then add resources which represent URL paths. Next, define HTTP methods like GET or POST on those resources. After that, integrate these methods with backend services such as Lambda functions or mock responses. Finally, deploy the API to a stage like 'prod' to make it accessible. Without deployment, the API is not live. This process ensures your API is structured, connected, and ready to handle requests.

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