301 and 302 redirects in Rest API - Time & Space Complexity

Time Complexity: 301 and 302 redirects

O(n)

Understanding Time Complexity

When a web server sends a 301 or 302 redirect, it tells the browser to go to a new address.

We want to understand how the time to handle these redirects grows as more redirects happen.

Scenario Under Consideration

Analyze the time complexity of handling chained redirects in a REST API.

GET /start
HTTP/1.1 302 Found
Location: /step1

GET /step1
HTTP/1.1 302 Found
Location: /step2

GET /step2
HTTP/1.1 301 Moved Permanently
Location: /final

GET /final
HTTP/1.1 200 OK
    

This shows a client following a chain of redirects until reaching the final URL.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Each redirect causes the client to make a new request.
• How many times: The number of redirects in the chain determines how many requests happen.

How Execution Grows With Input

Each additional redirect adds one more request and response cycle.

Input Size (redirects)	Approx. Operations (requests)
2	3 (2 redirects + 1 final request)
5	6 (5 redirects + 1 final request)
10	11 (10 redirects + 1 final request)

Pattern observation: The total requests grow linearly with the number of redirects.

Final Time Complexity

Time Complexity: O(n)

This means the time to complete the redirect process grows directly with the number of redirects.

Common Mistake

[X] Wrong: "Redirects happen instantly and don't add time."

[OK] Correct: Each redirect requires a new request and response, adding time that adds up with more redirects.

Interview Connect

Understanding how redirects affect request time helps you design efficient APIs and troubleshoot slow responses.

Self-Check

"What if the client cached the redirect targets? How would that change the time complexity?"

Practice

1. What does a 301 redirect indicate in a REST API?

easy

A. The resource has been deleted.

B. The resource is temporarily unavailable.

C. The resource has moved permanently to a new URL.

D. The resource requires authentication.

Solution

1. Step 1: Understand the meaning of 301 redirect

   A 301 redirect means the resource has moved permanently to a new location.

2. Step 2: Compare with other options

   Other options describe different HTTP statuses, not 301 redirect.

3. Final Answer:

   The resource has moved permanently to a new URL. -> Option C

4. Quick Check:

   301 redirect = permanent move [OK]

Hint: 301 means permanent move, 302 means temporary move [OK]

Common Mistakes:

• Confusing 301 with 302 redirect
• Thinking 301 means resource deleted
• Assuming 301 is for authentication

2. Which HTTP status code is used for a temporary redirect?

easy

A. 301

B. 302

C. 404

D. 500

Solution

1. Step 1: Identify status codes for redirects

   302 is the standard status code for temporary redirects.

2. Step 2: Eliminate other codes

   301 is permanent redirect, 404 is not found, 500 is server error.

3. Final Answer:

   302 -> Option B

4. Quick Check:

   Temporary redirect = 302 [OK]

Hint: 302 means temporary redirect, not 301 [OK]

Common Mistakes:

• Mixing 301 and 302 codes
• Choosing 404 or 500 by mistake
• Not knowing redirect codes

3. What will be the HTTP status code returned by this REST API snippet?

return Response(status=301, headers={'Location': 'https://newsite.com'})

medium

A. 301 Moved Permanently

B. 302 Found

C. 200 OK

D. 404 Not Found

Solution

1. Step 1: Analyze the status code in the response

   The code explicitly sets status=301, which means permanent redirect.

2. Step 2: Check the Location header

   The Location header points to the new URL, confirming redirect behavior.

3. Final Answer:

   301 Moved Permanently -> Option A

4. Quick Check:

   Status 301 with Location = permanent redirect [OK]

Hint: Status 301 with Location header means permanent redirect [OK]

Common Mistakes:

• Assuming 200 OK without checking status
• Confusing 301 with 302
• Ignoring Location header

4. Identify the error in this code snippet for a temporary redirect:

return Response(status=301, headers={'Location': 'https://temp.example.com'})

medium

A. Location header is missing.

B. Headers should not include Location.

C. Status code 301 is correct for temporary redirect.

D. Status code should be 302 for temporary redirect.

Solution

1. Step 1: Check status code for temporary redirect

   Temporary redirects require status code 302, not 301.

2. Step 2: Verify headers

   Location header is present and correct, so no error there.

3. Final Answer:

   Status code should be 302 for temporary redirect. -> Option D

4. Quick Check:

   Temporary redirect = 302, not 301 [OK]

Hint: Use 302 status for temporary redirects, not 301 [OK]

Common Mistakes:

• Using 301 instead of 302 for temporary redirects
• Omitting Location header
• Misunderstanding redirect status codes

5. You want to permanently redirect old API endpoints to new ones but keep temporary redirects for beta features. Which status codes should you use for each case?

hard

A. 301 for old endpoints, 302 for beta features

B. 302 for old endpoints, 301 for beta features

C. 404 for old endpoints, 302 for beta features

D. 500 for old endpoints, 301 for beta features

Solution

1. Step 1: Determine redirect type for old endpoints

   Old endpoints moved permanently, so use 301 status code.

2. Step 2: Determine redirect type for beta features

   Beta features are temporary, so use 302 status code.

3. Final Answer:

   301 for old endpoints, 302 for beta features -> Option A

4. Quick Check:

   Permanent = 301, Temporary = 302 [OK]

Hint: Permanent redirect = 301, temporary redirect = 302 [OK]

Common Mistakes:

• Swapping 301 and 302 codes
• Using error codes instead of redirects
• Not distinguishing permanent vs temporary