Webhook payload design in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this webhook payload validation code?

Consider a webhook payload validation function that checks if the payload contains the required fields event and timestamp. What will be the output of the following code when given the payload {"event": "user_signup", "timestamp": 1680000000}?

Rest API

def validate_payload(payload):
    required_fields = ['event', 'timestamp']
    for field in required_fields:
        if field not in payload:
            return f"Missing field: {field}"
    return "Payload valid"

payload = {"event": "user_signup", "timestamp": 1680000000}
print(validate_payload(payload))

A Payload valid

B Missing field: timestamp

C Missing field: event

D KeyError

💡 Hint

Check if all required keys exist in the payload dictionary.

The function checks for both 'event' and 'timestamp' keys. Since both are present, it returns 'Payload valid'.

🧠 Conceptual

intermediate

Which option best describes the purpose of including a signature in a webhook payload?

Why do webhook payloads often include a signature or hash value?

A To encrypt the payload data for privacy

B To compress the payload for faster transmission

C To verify the payload integrity and authenticity

D To format the payload as JSON

💡 Hint

Think about how the receiver can trust the source of the webhook.

The signature allows the receiver to verify that the payload was sent by a trusted source and was not altered during transmission.

🔧 Debug

advanced

What error does this webhook payload parsing code raise?

Given the following Python code that parses a webhook payload, what error will it raise?

Rest API

import json

def parse_payload(payload_str):
    data = json.loads(payload_str)
    return data['user']['id']

payload = '{"user": null}'
print(parse_payload(payload))

A KeyError

B TypeError

C ValueError

D AttributeError

💡 Hint

Consider what happens when you try to access a key on a NoneType object.

The 'user' key exists but its value is null (None in Python). Trying to access ['id'] on None causes a TypeError.

📝 Syntax

advanced

Which option produces the correct JSON payload with nested data?

Which of the following strings is a valid JSON payload representing a webhook event with nested user data?

A {"event": "order_created", "user": {"id": 123, "name": Alice}}

B {'event': 'order_created', 'user': {'id': 123, 'name': 'Alice'}}

C {"event": "order_created", "user": {id: 123, name: "Alice"}}

D {"event": "order_created", "user": {"id": 123, "name": "Alice"}}

💡 Hint

Remember JSON requires double quotes for keys and string values.

Option D uses double quotes correctly for keys and string values. Other options use single quotes or unquoted keys/values, which are invalid in JSON.

🚀 Application

expert

What is the number of top-level keys in this webhook payload?

Given the following webhook payload, how many top-level keys does it contain?

Rest API

{
  "event": "payment_received",
  "timestamp": 1680001234,
  "data": {
    "payment_id": "abc123",
    "amount": 49.99,
    "currency": "USD"
  },
  "metadata": {
    "customer_id": "cust789",
    "notes": "First payment"
  }
}

A 4

B 3

C 2

D 5

💡 Hint

Count only the keys at the outermost level of the JSON object.

The top-level keys are 'event', 'timestamp', 'data', and 'metadata', totaling 4 keys.

Practice

1. What is the main purpose of a webhook payload in a REST API?

easy

A. To store user login credentials securely

B. To create a user interface for the API

C. To send event details from one app to another automatically

D. To encrypt data between client and server

Solution

1. Step 1: Understand webhook payload role

   A webhook payload is a message sent automatically when an event happens, sharing event details.

2. Step 2: Compare options with webhook purpose

   Only To send event details from one app to another automatically describes sending event details automatically, which matches webhook payload use.

3. Final Answer:

   To send event details from one app to another automatically -> Option C

4. Quick Check:

   Webhook payload = event details sent automatically [OK]

Hint: Webhook payloads always send event info automatically [OK]

Common Mistakes:

• Confusing payload with user authentication
• Thinking payload creates UI
• Assuming payload encrypts data

2. Which of the following is the correct JSON structure for a webhook payload that includes event name and timestamp?

easy

A. [ "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" ]

B. { "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" }

C. { event = "user_signup", timestamp = "2024-06-01T12:00:00Z" }

D. "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z"

Solution

1. Step 1: Identify valid JSON syntax

   JSON objects use curly braces {}, keys and values separated by colon :, keys in double quotes, and comma between pairs.

2. Step 2: Check each option's syntax

   { "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" } uses correct JSON object syntax. [ "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" ] uses square brackets which denote arrays, not key-value pairs. { event = "user_signup", timestamp = "2024-06-01T12:00:00Z" } uses equals sign instead of colon. "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" is missing braces.

3. Final Answer:

   { "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" } -> Option B

4. Quick Check:

   Valid JSON object = { "event": "user_signup", "timestamp": "2024-06-01T12:00:00Z" } [OK]

Hint: JSON objects use braces and colons, not brackets or equals [OK]

Common Mistakes:

• Using square brackets instead of braces for objects
• Using equals sign instead of colon
• Omitting braces around JSON

3. Given this webhook payload JSON:

{"event": "order_created", "timestamp": "2024-06-01T15:30:00Z", "data": {"order_id": 123, "amount": 49.99}}

What value will the receiving app find for data.amount?

medium

A. 49.99

B. order_created

C. "amount"

D. 123

Solution

1. Step 1: Locate the data.amount field in JSON

   Inside the "data" object, the key "amount" has the value 49.99 (a number).

2. Step 2: Match the value to options

   49.99 matches the numeric value 49.99. Other options are either keys or unrelated values.

3. Final Answer:

   49.99 -> Option A

4. Quick Check:

   data.amount = 49.99 [OK]

Hint: Look inside nested 'data' object for 'amount' key [OK]

Common Mistakes:

• Confusing order_id with amount
• Selecting string key instead of value
• Choosing event name instead of data field

4. You receive this webhook payload:

{"event": "payment_failed", "timestamp": "2024-06-01T16:00:00Z", "data": {"payment_id": 789}}

What is wrong with this payload?

medium

A. Payment ID should be a string, not a number

B. Timestamp format is incorrect

C. Event name should be inside data object

D. Missing closing brace for the JSON object

Solution

1. Step 1: Check JSON completeness

   The payload ends without a closing brace '}' for the outermost JSON object, making it invalid JSON.

2. Step 2: Verify other parts

   Timestamp format is ISO 8601 and correct. Event name is correctly outside data. Payment ID can be number or string depending on design.

3. Final Answer:

   Missing closing brace for the JSON object -> Option D

4. Quick Check:

   JSON must have matching braces [OK]

Hint: Always check for matching braces in JSON payloads [OK]

Common Mistakes:

• Ignoring missing braces
• Assuming timestamp format is wrong
• Thinking event must be inside data

5. You want to design a webhook payload for a "user_deleted" event that includes the user ID and deletion reason. Which JSON payload design is best for clarity and easy parsing?

hard

A. { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "data": { "user_id": 456, "reason": "requested by user" } }

B. { "user_deleted": true, "user": 456, "reason": "requested by user" }

C. { "event": "user_deleted", "user_id": 456, "reason": "requested by user" }

D. { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "user": { "id": 456, "reason": "requested by user" } }

Solution

1. Step 1: Check for standard webhook fields

   { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "data": { "user_id": 456, "reason": "requested by user" } } includes event name, timestamp, and a nested data object holding user_id and reason, which is clear and standard.

2. Step 2: Compare other options for clarity and parsing

   { "user_deleted": true, "user": 456, "reason": "requested by user" } lacks event and timestamp keys properly named. { "event": "user_deleted", "user_id": 456, "reason": "requested by user" } mixes data fields at root level, less organized. { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "user": { "id": 456, "reason": "requested by user" } } nests reason inside user object, which is less intuitive.

3. Final Answer:

   { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "data": { "user_id": 456, "reason": "requested by user" } } -> Option A

4. Quick Check:

   Standard event + timestamp + data object = { "event": "user_deleted", "timestamp": "2024-06-01T17:00:00Z", "data": { "user_id": 456, "reason": "requested by user" } } [OK]

Hint: Use event, timestamp, and data object for clear payloads [OK]

Common Mistakes:

• Omitting timestamp
• Mixing data fields at root level
• Nesting unrelated fields inside user