[DEVELOPER] Advanced API Gateway

Question 1

What is the preferred and simpler integration type when integrating API Gateway with AWS Lambda?

Answer 1

Lambda Proxy Integration

Question 2

What is the major difference between Lambda Proxy and Lambda Non-Proxy (Custom) Integration.

Answer 2

• Proxy passes the entire request/response AS IS (all headers, body, etc.).
• Non-Proxy requires mapping templates to transform the data.

Question 3

What is the use case to use a VPC Link with API Gateway?

Answer 3

To connect API Gateway to private resources (like an ALB or NLB) located inside a VPC, allowing private connectivity without routing traffic over the public internet.

Question 4

What happens if the Mapping Template fails in a Lambda Non-Proxy Integration?

Answer 4

The request will fail before the Lambda function is ever invoked.

Question 5

What are the four types of API Gateway Authorizers?

Answer 5

1. IAM Roles/Policies
2. Cognito User Pools
3. Lambda Authorizers (Custom).
4. JWT Authorizers (ONLY IN HTTP APIs)

Question 6

What is the use case to use an API Gateway IAM Authorizer?

Answer 6

When the client is an authenticated AWS service or an IAM User

(e.g., an EC2 instance making a request using its attached role).

Question 7

What is the use case to use an API Gateway Cognito User Pool Authorizer?

Answer 7

When the client is a mobile or web application user that has authenticated via AWS Cognito

Question 8

What is the use case to use an API Gateway Lambda Authorizer?

Answer 8

When you need custom logic to validate a token or credentials

(e.g., integrating with a third-party OAuth provider or a custom legacy authentication system).

Question 9

How do you optimize the latency of an API Gateway Authorizer?

Answer 9

Configure the caching period for the authorization response

(e.g., cache the result for 300 seconds).

Question 10

How can you control access rates, define throttling limits, and monetize your API for third-party developers?

Answer 10

By configuring a Usage Plan and requiring clients to use API Keys.

Question 11

What is the purpose of an API Key in API Gateway?

Answer 11

It is a token that a client must include in their requests to identify the client and manage their access according to a Usage Plan.

Question 12

What is the difference between throttling limits configured on the Stage vs. the Usage Plan?

Answer 12

Usage Plan limits (Client-Side) override Stage limits (Server-Side), and Usage Plans are used for individual API consumers.

Question 13

What is the maximum size of a request body that API Gateway supports?

Answer 13

10 MB

Question 14

What is the first step required to make an API available to clients after making changes?

Answer 14

It must be deployed to a Stage.

Question 15

What is the primary service used to monitor the performance metrics, latency, and cache hit ratio of API Gateway?

Answer 15

Amazon CloudWatch

(look for Latency, 4XXErrors, and CacheHitCount metrics).

Question 16

You receive many 4XX errors for your API. What is the most likely cause?

Answer 16

Client-side errors

(e.g., incorrect resource path, missing authentication header, or throttling limits exceeded).

Question 17

You receive many 5XX errors for your API. What is the most likely cause?

Answer 17

Server-side errors

(e.g., Lambda function failures, or integration timeouts/errors).

Question 18

What are the two types of API supported by API Gateway? What is the difference in use case between them?

Answer 18

1. REST APIs are feature-rich
2. HTTP APIs are cheaper and support JWT Authorization natively

Question 19

Do API Gateway HTTP APIs support Usage Plans, API Keys, and Throttling?

Answer 19

No

Question 20

Do API Gateway REST APIs support Usage Plans, API Keys, and Throttling?

Answer 20

Yes

Question 21

Do API Gateway HTTP APIs support JWT Authorization tokens natively?

Answer 21

Yes

Question 22

Do API Gateway REST APIs support JWT Authorization Tokens natively?

Answer 22

No

You’ll need custom logic

Question 23

A developer needs to configure an API Gateway to route requests to different Lambda functions based on a version number in the header. What is the best way?

Answer 23

Use API Gateway Stage Variables.

Question 24

A developer needs to configure a custom endpoint for API Gateway that terminates the connection with a mutual TLS (mTLS) requirement. Which component is responsible for verifying the client certificate?

Answer 24

The API Gateway Custom Domain Name configuration

Question 25

A developer is creating a REST API using API Gateway. The API must support multiple versions (e.g., v1, v2) accessible via different URLs. What is the most efficient way to achieve this?

Answer 25

Clone the API definition and deploy it to a new Stage, OR use distinct Resource paths (e.g., /v1, /v2) in a single API. ## Footnote Using distinct resource trees (/v1/users, /v2/users) allows side-by-side execution in the same stage, or cloning creates a clean separation.

Question 26

What is the maximum execution duration for an API Gateway Lambda proxy integration before it times out?

Answer 26

**29 seconds**

Question 27

You are using API Gateway. You want to route requests to different backend endpoints based on a header value (e.g., x-client-type). Which feature is best?

Answer 27

Use a Lambda function as a proxy to route the request logic. ## Footnote API Gateway does not natively support conditional routing to different integrations based on headers (unlike ALB). You typically route to a Lambda which then calls the appropriate logic, or use multiple resources.