HTTP methods (GET, POST, PUT, DELETE) in Flask - Performance & Optimization

Performance: HTTP methods (GET, POST, PUT, DELETE)

MEDIUM IMPACT

This affects how fast the server responds and how much data is sent or received, impacting page load and interaction speed.

Sending data to update a resource on the server

Flask

from flask import Flask, request
app = Flask(__name__)

@app.route('/update', methods=['PUT'])
def update():
    data = request.get_json()
    # process update
    return 'Updated', 200

PUT sends data in the request body, allowing larger payloads and proper caching behavior, improving response speed and security.

📈 Performance GainReduces caching issues and avoids URL length limits, improving server response time

Sending data to update a resource on the server

Flask

from flask import Flask, request
app = Flask(__name__)

@app.route('/update', methods=['GET'])
def update():
    data = request.args.get('data')
    # process update
    return 'Updated', 200

Using GET to update data sends data in the URL, which is limited in size and can be cached or logged, causing security and performance issues.

📉 Performance CostCan cause unnecessary caching and slow server response due to URL length limits

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
GET for fetching data	Minimal	0	Low	[OK] Good
POST for fetching data	Minimal	0	Low	[X] Bad
PUT for updating data	Minimal	0	Low	[OK] Good
GET for updating data	Minimal	0	Low	[X] Bad
DELETE for deleting data	Minimal	0	Low	[OK] Good
GET for deleting data	Minimal	0	Low	[X] Bad

Rendering Pipeline

HTTP methods affect how the browser and server communicate, influencing the time to first byte and content delivery, which impacts the rendering pipeline stages.

→Network Request

→Server Processing

→Content Download

→Render Tree Construction

⚠️ BottleneckServer Processing

Core Web Vital Affected

LCP

This affects how fast the server responds and how much data is sent or received, impacting page load and interaction speed.

Optimization Tips

1Use GET for fetching data to enable caching and faster load times.

2Use POST or PUT for sending or updating data to avoid URL length limits and caching issues.

3Use DELETE for removing resources to prevent accidental actions and improve user experience.

Performance Quiz - 3 Questions

Which HTTP method is best for retrieving data without changing server state?

A PUT

B POST

C GET

D DELETE

DevTools: Network

How to check: Open DevTools, go to Network tab, perform the action, and check the HTTP method column for the request.

What to look for: Ensure the HTTP method matches the action (GET for fetch, POST/PUT for send/update, DELETE for delete) to confirm proper usage.

Practice

1. Which HTTP method is typically used in Flask to retrieve data without changing anything on the server?

easy

A. PUT

B. POST

C. GET

D. DELETE

Solution

1. Step 1: Understand HTTP methods purpose

   GET is used to request data without modifying it, so it is safe and idempotent.

2. Step 2: Match method to Flask usage

   In Flask, GET routes are used to send data back to the client without changing server state.

3. Final Answer:

   GET -> Option C

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET reads data, POST creates, PUT updates, DELETE removes [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE to get data
• Thinking PUT is for reading data

2. Which of the following Flask route definitions correctly allows handling both GET and POST methods?

easy

A. @app.route('/submit', allow_methods=['GET', 'POST'])

B. @app.route('/submit', methods=['GET', 'POST'])

C. @app.route('/submit', methods='GET, POST')

D. @app.route('/submit', method=['GET', 'POST'])

Solution

1. Step 1: Recall Flask route syntax for methods

   Flask uses the 'methods' keyword argument as a list of strings to specify allowed HTTP methods.

2. Step 2: Check each option's syntax

   @app.route('/submit', methods=['GET', 'POST']) correctly uses methods=['GET', 'POST']. Others have wrong keywords or wrong data types.

3. Final Answer:

   @app.route('/submit', methods=['GET', 'POST']) -> Option B

4. Quick Check:

   Correct keyword and list format = @app.route('/submit', methods=['GET', 'POST']) [OK]

Hint: Use methods=['GET', 'POST'] exactly in route decorator [OK]

Common Mistakes:

• Using 'method' instead of 'methods'
• Passing methods as a string instead of list
• Using unknown keywords like 'allow_methods'

3. What will be the output when a client sends a DELETE request to this Flask route?

@app.route('/item/', methods=['DELETE'])
def delete_item(id):
    return f"Deleted item {id}", 200

medium

A. "Deleted item <id>" with status 200

B. 404 Not Found error

C. Method Not Allowed error

D. Empty response with status 204

Solution

1. Step 1: Analyze route and method

   The route accepts DELETE requests with an integer id parameter and returns a string with status 200.

2. Step 2: Understand response for DELETE request

   Since the method matches and function returns a message with 200, the client receives that message and status.

3. Final Answer:

   "Deleted item <id>" with status 200 -> Option A

4. Quick Check:

   DELETE request handled correctly = "Deleted item <id>" with status 200 [OK]

Hint: Route method matches request method, so response is returned [OK]

Common Mistakes:

• Expecting 404 if route exists
• Confusing DELETE with GET behavior
• Assuming empty response without checking code

4. Identify the error in this Flask route that should handle PUT requests:

@app.route('/update', methods=['PUT'])
def update():
    data = request.get_json()
    return 'Updated', 200

medium

A. Missing import of 'request' from Flask

B. Incorrect HTTP method name 'PUT'

C. Route decorator syntax is invalid

D. Function must return JSON, not string

Solution

1. Step 1: Check usage of 'request'

   The function uses 'request.get_json()' but 'request' is not imported from Flask, causing a NameError.

2. Step 2: Verify other parts

   Method 'PUT' is valid, route syntax is correct, and returning string with status 200 is allowed.

3. Final Answer:

   Missing import of 'request' from Flask -> Option A

4. Quick Check:

   Using 'request' without import causes error [OK]

Hint: Always import 'request' to access request data [OK]

Common Mistakes:

• Forgetting to import 'request'
• Thinking PUT is invalid method
• Assuming string return is wrong

5. You want to create a Flask API endpoint to update a user's email using PUT and delete the user using DELETE at the same URL '/user/'. Which is the best way to define this in Flask?

hard

A. Use GET method for both update and delete actions

B. Create two separate routes with different URLs for PUT and DELETE

C. Use only POST method and check a hidden field for action

D. Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function

Solution

1. Step 1: Understand RESTful design

   PUT and DELETE are standard methods for update and delete at the same resource URL.

2. Step 2: Implement in Flask

   Flask allows one route to handle multiple methods; inside the function, you check request.method to run correct code.

3. Final Answer:

   Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function -> Option D

4. Quick Check:

   Multiple methods on one route with method check = Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function [OK]

Hint: One route, multiple methods, check request.method inside [OK]

Common Mistakes:

• Creating separate URLs for same resource actions
• Using POST or GET incorrectly for update/delete
• Not checking request.method inside route