API Gateway throttling in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is API Gateway throttling?

API Gateway throttling is a way to limit the number of requests a client can make to an API in a given time. It helps protect the backend from too much traffic and keeps the system stable.

beginner

What are the two main throttling limits in AWS API Gateway?

The two main limits are the rate limit (requests per second) and the burst limit (maximum number of requests allowed in a short time).

intermediate

How does burst capacity help in API Gateway throttling?

Burst capacity allows short spikes of traffic above the steady rate limit. It acts like a temporary buffer to handle sudden bursts without rejecting requests immediately.

beginner

What happens when a client exceeds the throttling limits in API Gateway?

The API Gateway returns a 429 Too Many Requests error to the client, indicating the request was rejected due to throttling.

intermediate

How can you customize throttling settings per API key in AWS API Gateway?

You can create usage plans that specify throttling limits and associate them with API keys. This allows different clients to have different rate and burst limits.

What does the burst limit in API Gateway throttling control?

A Number of concurrent connections

B Total requests per day

C Maximum requests allowed in a short time

D Size of the request payload

The burst limit controls how many requests can be handled in a short burst above the steady rate limit.

What HTTP status code does API Gateway return when throttling limits are exceeded?

A 429 Too Many Requests

B 500 Internal Server Error

C 403 Forbidden

D 404 Not Found

API Gateway returns 429 to indicate the client sent too many requests in a given time.

Which AWS feature allows setting different throttling limits for different clients?

A IAM Roles

B Usage Plans with API Keys

C Lambda Functions

D CloudWatch Alarms

Usage plans let you define throttling and quota limits and associate them with API keys for different clients.

Why is throttling important in API Gateway?

A To encrypt API requests

B To increase API response size

C To speed up database queries

D To protect backend from overload

Throttling protects backend services by limiting request rates and preventing overload.

If your API experiences sudden traffic spikes, which throttling setting helps handle them temporarily?

A Burst limit

B Timeout setting

C Rate limit

D Cache size

Burst limit allows short bursts of traffic above the steady rate limit to handle spikes.

Explain how API Gateway throttling works and why it is important for system stability.

Think about how limiting requests helps keep the system healthy.

Describe how you can customize throttling for different clients using AWS API Gateway features.

Consider how different users might have different access needs.

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