Webhook registration endpoint in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this webhook registration response?

Consider a webhook registration endpoint that returns a JSON response confirming the registration. What will be the output of the following code snippet when the webhook is successfully registered?

Rest API

response = {
  "status": "success",
  "message": "Webhook registered successfully",
  "webhook_id": 12345
}
print(response)

A {"status": "success", "message": "Webhook registered successfully", "webhook_id": 12345}

B {'status': 'success', 'message': 'Webhook registered successfully', 'webhook_id': 12345}

C Webhook registered successfully with ID 12345

D Error: webhook_id missing

💡 Hint

Look at how Python prints dictionaries.

The code prints the Python dictionary as is, which uses single quotes for keys and string values.

🧠 Conceptual

intermediate

Which HTTP method is typically used to register a webhook?

When creating a webhook registration endpoint, which HTTP method should be used to send the registration request?

A POST

B GET

C DELETE

D PUT

💡 Hint

Think about sending data to create a new resource.

POST is used to create new resources or submit data to the server, which fits webhook registration.

🔧 Debug

advanced

What error does this webhook registration code raise?

This Python Flask code snippet is intended to register a webhook but raises an error. What error does it raise?

Rest API

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

@app.route('/register_webhook', methods=['POST'])
def register_webhook():
    data = request.json
    url = data['url']
    if not url.startswith('http'):
        return jsonify({'error': 'Invalid URL'}), 400
    # Save webhook logic here
    return jsonify({'status': 'success', 'webhook_url': url})

# Missing app.run() call

A TypeError: 'str' object is not callable

B RuntimeError: Working outside of request context

C AttributeError: 'NoneType' object has no attribute 'startswith'

D No error, runs successfully

💡 Hint

Check what happens if request.json is None.

If the request body is empty or not JSON, request.json is None, so data['url'] raises TypeError because None is not subscriptable. But here the error is AttributeError because url is None and calling startswith on None fails.

📝 Syntax

advanced

Which option contains the correct JSON schema snippet for webhook registration?

You want to define a JSON schema for validating webhook registration data. Which option is syntactically correct?

A

{
  "type": "object",
  "properties": {
    "url": {"type": "string", "format": "uri"},
    "events": {"type": "array", "items": {"type": "string"}}
  },
  "required": [url, events]
}

B

{
  type: "object",
  properties: {
    url: {type: "string", format: "uri"},
    events: {type: "array", items: {type: "string"}}
  },
  required: ["url", "events"]
}

C

{
  "type": "object",
  "properties": {
    "url": {"type": "string", "format": "uri"},
    "events": {"type": "array", "items": {"type": "string"}}
  },
  required: ["url", "events"]
}

D

{
  "type": "object",
  "properties": {
    "url": {"type": "string", "format": "uri"},
    "events": {"type": "array", "items": {"type": "string"}}
  },
  "required": ["url", "events"]
}

💡 Hint

JSON keys and string values must be in double quotes.

Option D uses correct JSON syntax with double quotes around keys and string values, including the required array.

🚀 Application

expert

What is the number of unique events registered after these webhook registrations?

Assume a webhook registration system where each registration includes a list of events. Given these three registrations, how many unique events are registered in total? Registration 1: events = ["create", "update"] Registration 2: events = ["delete", "update"] Registration 3: events = ["create", "archive"]

A 4

B 5

C 3

D 6

💡 Hint

Count each event only once across all registrations.

The unique events are create, update, delete, archive. That's 4 unique events, but careful: create, update, delete, archive = 4, so answer is 4.

Practice

1.

What is the main purpose of a webhook registration endpoint in a REST API?

easy

A. To update the API documentation automatically

B. To send event data directly to all users

C. To store user login credentials securely

D. To let apps register their callback URL to receive event updates

Solution

1. Step 1: Understand webhook registration

   A webhook registration endpoint allows external apps to tell your system where to send event notifications.

2. Step 2: Identify the main function

   The main function is to register a callback URL and event type so your system knows where to send updates.

3. Final Answer:

   To let apps register their callback URL to receive event updates -> Option D

4. Quick Check:

   Webhook registration = register callback URL [OK]

Hint: Webhook registration means saving callback URLs for events [OK]

Common Mistakes:

• Confusing webhook registration with sending events
• Thinking it stores user credentials
• Assuming it updates documentation

2.

Which HTTP method is typically used to register a webhook endpoint?

easy

A. POST

B. GET

C. DELETE

D. PUT

Solution

1. Step 1: Recall HTTP methods for creating resources

   POST is used to send data to the server to create a new resource, like registering a webhook.

2. Step 2: Eliminate other methods

   GET retrieves data, DELETE removes data, PUT updates existing data. Registration is creation, so POST fits best.

3. Final Answer:

   POST -> Option A

4. Quick Check:

   Register webhook = POST request [OK]

Hint: Use POST to send data and create webhook registrations [OK]

Common Mistakes:

• Using GET instead of POST for registration
• Confusing PUT with POST
• Using DELETE by mistake

3.

Given this JSON payload sent to a webhook registration endpoint:
{"callback_url": "https://example.com/hook", "event": "order_created"}
What should the server respond if the registration is successful?

medium

A. {"status": "success", "message": "Webhook registered"}

B. {"error": "Invalid URL"}

C. {"status": "failed", "message": "Missing event type"}

D. {"status": "success", "message": "Webhook deleted"}

Solution

1. Step 1: Analyze the input payload

   The payload contains a valid callback URL and an event type, so it should be accepted.

2. Step 2: Determine expected success response

   On success, the server confirms registration with a success status and message.

3. Final Answer:

   {"status": "success", "message": "Webhook registered"} -> Option A

4. Quick Check:

   Valid input = success confirmation [OK]

Hint: Success means status success and confirmation message [OK]

Common Mistakes:

• Confusing error messages as success
• Ignoring missing fields
• Mixing registration and deletion messages

4.

Consider this snippet of a webhook registration handler in Python Flask:

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

@app.route('/register', methods=['POST'])
def register_webhook():
    data = request.json
    if 'callback_url' not in data or 'event' not in data:
        return jsonify({'error': 'Missing fields'}), 400
    # Assume registration logic here
    return jsonify({'status': 'success', 'message': 'Webhook registered'})

What error will occur if the client sends an empty POST body?

medium

A. No error, returns success

B. TypeError because request.json is a string

C. TypeError because data is None and keys are accessed

D. 404 Not Found error

Solution

1. Step 1: Understand request.json behavior on empty body

   If the POST body is empty, request.json returns None, not a dictionary.

2. Step 2: Analyze the if condition

   The code tries to check keys in data, but data is None, so 'in' operation causes a TypeError.

3. Final Answer:

   TypeError because data is None and keys are accessed -> Option C

4. Quick Check:

   Empty body means request.json is None causing key access error [OK]

Hint: Empty JSON body makes request.json None, causing TypeError [OK]

Common Mistakes:

• Assuming empty body returns empty dict
• Expecting success without data
• Confusing error types

5.

You want to build a webhook registration endpoint that only accepts URLs starting with https:// and event types from a fixed list: ["order_created", "order_shipped"]. Consider this Python validation function:

def validate_webhook(data):
    callback = data.get('callback_url')
    event = data.get('event')
    if not callback.startswith('https://'):
        return False
    if event not in ['order_created', 'order_shipped']:
        return False
    return True

Which statement best describes its behavior?

hard

A. Correctly validates both URL scheme and event type

B. Fails if callback_url is missing, causing AttributeError

C. Allows any URL scheme, no validation done

D. Only checks event type, ignores URL

Solution

1. Step 1: Check callback_url usage

   The code calls startswith on callback without checking if callback is None, so if missing, it raises AttributeError.

2. Step 2: Verify event type check

   The event type check is correct, but the missing callback check causes failure before this.

3. Final Answer:

   Fails if callback_url is missing, causing AttributeError -> Option B

4. Quick Check:

   Missing callback_url causes error on startswith call [OK]

Hint: Check for None before calling string methods to avoid errors [OK]

Common Mistakes:

• Not checking if callback_url exists before startswith
• Assuming event type validation covers all errors
• Ignoring input validation order