429 Too Many Requests in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the HTTP status code returned?

You have a REST API that limits clients to 5 requests per minute. If a client sends 6 requests quickly, what HTTP status code will the server return for the 6th request?

A 429 Too Many Requests

B 200 OK

C 500 Internal Server Error

D 403 Forbidden

💡 Hint

Think about what status code means the client sent too many requests in a short time.

The 429 status code means the client has sent too many requests in a given amount of time, triggering rate limiting.

🧠 Conceptual

intermediate

Why use 429 Too Many Requests status code?

Which reason best explains why an API uses the 429 Too Many Requests status code?

A To confirm the request was successful

B To show the server encountered an unexpected error

C To indicate the client is not authorized

D To tell the client to slow down because it exceeded request limits

💡 Hint

Think about what happens when a client sends too many requests too fast.

429 status code tells the client to slow down because it has sent too many requests in a short time.

🔧 Debug

advanced

Identify the cause of unexpected 429 errors

A client reports receiving 429 Too Many Requests errors even though they send only 1 request per minute. What is the most likely cause?

A The client is not authorized to access the API

B The client is sending requests too slowly

C The server's rate limit is set too low or misconfigured

D The server is down and returning 429 by mistake

💡 Hint

Consider server settings that control request limits.

If the server's rate limit is too low or misconfigured, it may block even low-frequency requests with 429 errors.

🚀 Application

advanced

How to handle 429 errors in client code?

You receive a 429 Too Many Requests response from an API. What is the best way for your client application to handle this?

A Wait for the time specified in the Retry-After header before retrying

B Stop sending requests permanently

C Immediately retry the request without delay

D Ignore the error and continue sending requests

💡 Hint

Look for a header that tells you when to try again.

The Retry-After header tells the client how long to wait before retrying after a 429 response.

❓ Predict Output

expert

What is the output of this rate limiting code snippet?

Consider this Python Flask snippet implementing simple rate limiting. What will be the output on the 4th request from the same IP within 10 seconds?

Rest API

from flask import Flask, request, jsonify
import time

app = Flask(__name__)

request_times = {}

@app.route('/api')
def api():
    ip = request.remote_addr
    now = time.time()
    times = request_times.get(ip, [])
    # Remove timestamps older than 10 seconds
    times = [t for t in times if now - t < 10]
    if len(times) >= 3:
        return jsonify({'error': 'Too many requests'}), 429
    times.append(now)
    request_times[ip] = times
    return jsonify({'message': 'Success'})

# Simulate 4 requests from same IP quickly
ip = '192.168.1.1'
for i in range(4):
    request_times[ip] = [time.time() - 1, time.time() - 2, time.time() - 3]
    now = time.time()
    times = request_times.get(ip, [])
    times = [t for t in times if now - t < 10]
    if len(times) >= 3:
        print(429)
    else:
        times.append(now)
        request_times[ip] = times
        print(200)

A

200
200
200
200

B

200
200
200
429

C

429
429
429
429

D

200
429
429
429

💡 Hint

Check how many timestamps are kept and when 429 is returned.

The code allows 3 requests within 10 seconds. The 4th request triggers 429.