Burst and nodelay options in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the burst option in nginx rate limiting

What does the burst option do in the nginx limit_req directive?

A Allows a client to exceed the rate limit by a specified number of requests temporarily.

B Immediately rejects requests that exceed the rate limit without delay.

C Sets the maximum number of requests allowed per second.

D Disables rate limiting for burst traffic.

💡 Hint

Think about how nginx handles sudden spikes in requests.

The burst option lets nginx queue extra requests beyond the rate limit temporarily, allowing short bursts of traffic without immediate rejection.

🧠 Conceptual

intermediate

Effect of the nodelay option in nginx rate limiting

What is the effect of adding the nodelay option to the limit_req directive in nginx?

A Requests exceeding the burst limit are delayed before processing.

B Requests within the burst limit are processed immediately without delay.

C Disables the burst option entirely.

D Causes nginx to reject all requests immediately.

💡 Hint

Consider how nodelay changes request handling timing.

With nodelay, requests within the burst limit are not delayed but processed immediately, allowing faster handling of bursts.

💻 Command Output

advanced

Output of nginx error log with burst and nodelay

Given this nginx configuration snippet:

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s;
limit_req zone=mylimit burst=3 nodelay;

What will the error log show if a client sends 5 requests instantly?

A Only 1 request is accepted immediately; the rest are rejected.

B All 5 requests are delayed and accepted without errors.

C The first 4 requests are accepted immediately; the 5th request is rejected with 503 error.

D All 5 requests are rejected immediately.

💡 Hint

Remember the burst allows extra requests beyond the rate, and nodelay processes them immediately.

The rate is 1 request per second, burst=3 allows 3 extra requests, so 4 requests are accepted immediately. The 5th exceeds burst and is rejected with 503.

❓ Troubleshoot

advanced

Troubleshooting unexpected delays with burst and nodelay

An nginx server uses limit_req zone=mylimit burst=5; without nodelay. Clients report delays even when sending requests within burst limit. Why?

A The rate limit is set too high, causing delays.

B Nginx is rejecting requests instead of delaying them.

C The burst option is ignored without nodelay, so all requests are delayed.

D Requests within burst are delayed to smooth traffic, causing perceived delays.

💡 Hint

Think about how nginx handles queued requests without nodelay.

Without nodelay, requests within burst are delayed to spread them evenly, which can cause delays clients notice.

✅ Best Practice

expert

Choosing burst and nodelay settings for a high-traffic API

You manage a high-traffic API and want to allow short bursts of up to 10 requests without delay but reject any requests beyond that immediately. Which nginx configuration is best?

A limit_req zone=api burst=10 nodelay;

B limit_req zone=api burst=10;

C limit_req zone=api burst=5 nodelay;

D limit_req zone=api burst=10 delay=0;

💡 Hint

Consider how to allow bursts without delay and reject excess requests.

Using burst=10 with nodelay allows up to 10 requests to be processed immediately. Requests beyond 10 are rejected. Option A is invalid syntax; option A delays burst requests; option A allows fewer bursts.