API Gateway throttling in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding API Gateway Throttling Limits

What is the default rate limit for AWS API Gateway throttling per account per region?

A 100,000 requests per second

B 1,000 requests per second

C 10,000 requests per second

D 5,000 requests per second

💡 Hint

Think about the default soft limits AWS sets for API Gateway to protect backend services.

AWS API Gateway has a default regional throttling limit of 5,000 requests per second per account. This helps prevent backend overload.

❓ Architecture

intermediate

Designing Throttling for Multiple API Stages

You have multiple stages (dev, test, prod) in your API Gateway. How can you apply throttling limits independently for each stage?

A Apply throttling only at the account level, stages share the same limits

B Use Lambda authorizers to enforce throttling per stage

C Set usage plans with API keys scoped to each stage

D Create separate API Gateway accounts for each stage

💡 Hint

Think about how usage plans and API keys can control access and limits per stage.

Usage plans with API keys allow you to set throttling and quota limits per stage by associating keys with specific stages.

❓ scaling

advanced

Handling Bursty Traffic with API Gateway Throttling

Your API experiences sudden bursts of traffic exceeding the throttling limits. Which approach best helps to handle this without dropping requests?

A Enable burst capacity and use usage plans with quotas

B Increase the throttling limits manually without any other changes

C Disable throttling to allow all requests through

D Use CloudFront in front of API Gateway to cache responses

💡 Hint

Consider AWS features that allow temporary traffic spikes without rejecting requests.

API Gateway supports burst capacity to handle sudden traffic spikes temporarily. Usage plans with quotas help manage overall usage.

❓ tradeoff

advanced

Tradeoffs of Client-Side vs Server-Side Throttling

Which is a key tradeoff when choosing client-side throttling over server-side throttling in API Gateway?

A Client-side throttling guarantees no requests are dropped by the server

B Client-side throttling reduces server load but relies on client compliance

C Server-side throttling requires clients to implement retry logic

D Server-side throttling cannot be configured in API Gateway

💡 Hint

Think about control and reliability differences between client and server throttling.

Client-side throttling reduces load on the server but depends on clients to respect limits, which may not always happen.

❓ estimation

expert

Estimating Maximum Requests with Throttling and Burst Capacity

Your API Gateway has a steady rate limit of 5,000 requests per second and a burst capacity of 10,000 requests. How many requests can it handle in 2 seconds during a sudden traffic spike?

A 20,000 requests

B 15,000 requests

C 10,000 requests

D 5,000 requests

💡 Hint

Consider how burst capacity adds to the steady rate limit over time.

In the first second, API Gateway can handle up to 15,000 requests (10,000 burst + 5,000 steady), and 5,000 steady requests in the second second, totaling 20,000 requests over 2 seconds.

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