API Gateway throttling in AWS - Mini Project: Build & Apply

API Gateway Throttling Configuration

📖 Scenario: You are managing an API for a small online store. To protect your backend from too many requests at once, you want to set up throttling limits on your API Gateway. This will help keep your service stable and responsive for all users.

🎯 Goal: Configure an AWS API Gateway REST API with throttling limits that restrict the number of requests per second and burst capacity.

📋 What You'll Learn

Create an API Gateway REST API resource named MyApi.

Set a stage named prod for the API.

Configure throttling limits with a rate limit of 100 requests per second and a burst limit of 200.

Use AWS CloudFormation YAML syntax for the configuration.

💡 Why This Matters

🌍 Real World

API Gateway throttling is used to protect backend services from overload by limiting the number of requests clients can make in a given time.

💼 Career

Cloud engineers and DevOps professionals often configure throttling to ensure APIs remain reliable and performant under varying traffic loads.

1

Create the API Gateway REST API resource

Create a CloudFormation resource named MyApi of type AWS::ApiGateway::RestApi with the property Name set to MyApi.

AWS

# Your code here

Hint

Use the Resources section to define your API Gateway REST API resource.

2

Add the deployment stage configuration

Add a CloudFormation resource named MyApiStage of type AWS::ApiGateway::Stage with the properties StageName set to prod and RestApiId referencing MyApi.

AWS

Resources:
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApi
# Your code here

Hint

Use !Ref MyApi to link the stage to the API.

3

Add throttling limits configuration

In the MyApiStage resource, add the MethodSettings property with a list containing one item. This item should have ResourcePath set to "/*", HttpMethod set to "*", and ThrottlingRateLimit set to 100 and ThrottlingBurstLimit set to 200.

AWS

Resources:
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApi
  MyApiStage:
    Type: AWS::ApiGateway::Stage
    Properties:
      StageName: prod
      RestApiId: !Ref MyApi
      # Your code here

Hint

Use MethodSettings to configure throttling for all methods and resources.

4

Complete the CloudFormation template

Add the AWSTemplateFormatVersion set to "2010-09-09" at the top of the template to complete the CloudFormation YAML configuration.

AWS

# Your code here
Resources:
  MyApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: MyApi
  MyApiStage:
    Type: AWS::ApiGateway::Stage
    Properties:
      StageName: prod
      RestApiId: !Ref MyApi
      MethodSettings:
        - ResourcePath: "/*"
          HttpMethod: "*"
          ThrottlingRateLimit: 100
          ThrottlingBurstLimit: 200

Hint

The AWSTemplateFormatVersion is required at the top of every CloudFormation template.

Practice

1. What is the primary purpose of API Gateway throttling in AWS?

easy

A. To store API request logs permanently

B. To limit the number of requests to protect backend services from overload

C. To increase the speed of API responses

D. To encrypt API requests automatically

Solution

1. Step 1: Understand API Gateway throttling purpose

   API Gateway throttling is designed to control the rate of incoming requests to prevent backend overload.

2. Step 2: Evaluate options against throttling purpose

   Only To limit the number of requests to protect backend services from overload correctly describes throttling as limiting requests to protect backend services.

3. Final Answer:

   To limit the number of requests to protect backend services from overload -> Option B

4. Quick Check:

   Throttling = Limit requests [OK]

Hint: Throttling means limiting requests to avoid overload [OK]

Common Mistakes:

• Confusing throttling with encryption
• Thinking throttling speeds up responses
• Assuming throttling stores logs

2. Which of the following correctly represents the syntax to set a rate limit of 100 requests per second in AWS API Gateway throttling settings?

easy

A. throttle(100, 200)

B. rate_limit = 100, burst_limit = 200

C. rateLimit: 100, burstLimit: 200

D. setRate(100), setBurst(200)

Solution

1. Step 1: Identify correct AWS API Gateway throttling syntax

   The correct syntax uses camelCase keys like rateLimit and burstLimit with numeric values.

2. Step 2: Compare options to AWS documentation style

   rateLimit: 100, burstLimit: 200 matches the correct syntax format; others use invalid or pseudo-code styles.

3. Final Answer:

   rateLimit: 100, burstLimit: 200 -> Option C

4. Quick Check:

   Correct syntax uses camelCase keys [OK]

Hint: AWS uses camelCase keys like rateLimit, burstLimit [OK]

Common Mistakes:

• Using underscores instead of camelCase
• Using function calls instead of key-value pairs
• Confusing method names with settings

3. Given the following API Gateway throttling settings: rateLimit: 50 and burstLimit: 100, what happens when 120 requests arrive simultaneously?

medium

A. Up to 100 requests are processed immediately; the rest are throttled

B. Only 50 requests are processed; the rest are throttled

C. All 120 requests are processed immediately

D. Requests are queued and processed one by one without throttling

Solution

1. Step 1: Understand burstLimit and rateLimit roles

   BurstLimit allows short spikes up to 100 requests at once; rateLimit controls steady rate at 50 requests per second.

2. Step 2: Analyze 120 simultaneous requests

   Up to 100 requests are allowed immediately (burst), the remaining 20 exceed burst and get throttled.

3. Final Answer:

   Up to 100 requests are processed immediately; the rest are throttled -> Option A

4. Quick Check:

   BurstLimit = immediate spike limit [OK]

Hint: BurstLimit allows short spikes, rateLimit steady rate [OK]

Common Mistakes:

• Confusing rateLimit with burstLimit
• Assuming all requests pass immediately
• Thinking requests queue without throttling

4. You configured API Gateway throttling with rateLimit: 200 and burstLimit: 300. However, clients report receiving HTTP 429 errors even when sending 150 requests per second. What is the most likely cause?

medium

A. The usage plan or API key limits are lower than throttling settings

B. The API Gateway cache is full, causing throttling

C. The backend service is down, causing 429 errors

D. The rateLimit and burstLimit values are too high

Solution

1. Step 1: Understand causes of HTTP 429 in API Gateway

   429 errors mean throttling triggered due to exceeding limits.

2. Step 2: Check usage plan and API key limits

   Usage plans or API keys can have lower throttling limits overriding global settings, causing 429 errors at lower rates.

3. Final Answer:

   The usage plan or API key limits are lower than throttling settings -> Option A

4. Quick Check:

   Usage plan limits override throttling [OK]

Hint: Check usage plan limits if throttling occurs unexpectedly [OK]

Common Mistakes:

• Blaming backend service for 429 errors
• Assuming cache affects throttling
• Thinking high limits cause throttling

5. You design an API for a popular mobile app expecting sudden traffic spikes up to 1000 requests per second for short bursts, but steady traffic around 300 requests per second. How should you configure API Gateway throttling to handle this efficiently?

hard

A. Set rateLimit to 1000 and burstLimit to 300

B. Set both rateLimit and burstLimit to 1000

C. Set both rateLimit and burstLimit to 300

D. Set rateLimit to 300 and burstLimit to 1000

Solution

1. Step 1: Match throttling settings to traffic patterns

   RateLimit controls steady request rate; BurstLimit allows short spikes above steady rate.

2. Step 2: Apply to given traffic

   Set rateLimit to steady 300 requests/sec and burstLimit to 1000 for short spikes.

3. Final Answer:

   Set rateLimit to 300 and burstLimit to 1000 -> Option D

4. Quick Check:

   RateLimit steady, BurstLimit spike [OK]

Hint: RateLimit steady rate, BurstLimit handles spikes [OK]

Common Mistakes:

• Swapping rateLimit and burstLimit values
• Setting both limits too low
• Ignoring burstLimit for spikes