Why API design affects system usability in HLD - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a REST API endpoint that returns user data.

HLD

GET /users/[1]

Drag options to blanks, or click blank then click option'

Alist

Bprofile

Cdelete

Dupdate

Attempts:

3 left

💡 Hint

Common Mistakes

Using verbs like 'delete' or 'update' in a GET request endpoint.

The endpoint /users/profile is commonly used to fetch user data, making the API intuitive and usable.

2fill in blank

medium

Complete the code to specify the HTTP method for creating a new resource in REST API.

HLD

HTTP Method: [1] /items

Drag options to blanks, or click blank then click option'

APOST

BGET

CDELETE

DPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing POST with GET or DELETE methods.

The POST method is used to create new resources, which is a key part of API usability by following standards.

3fill in blank

hard

Fix the error in the API response format to improve usability.

HLD

{ "status": "success", "data": [1] }

Drag options to blanks, or click blank then click option'

A[{"id":1,"name":"Alice"}]

Bnull

C"user"

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a string or null instead of structured data.

The data field should contain a list of user objects for clarity and consistency in API responses.

4fill in blank

hard

Fill both blanks to create a clear and consistent API error response.

HLD

{ "error_code": [1], "message": "[2]" }

Drag options to blanks, or click blank then click option'

A404

B500

CNot Found

DInternal Server Error

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing error codes and messages that don't correspond.

A 404 error code with message Not Found clearly informs the user about the missing resource, improving usability.

5fill in blank

hard

Fill all three blanks to design an API endpoint with versioning and resource identification.

HLD

"/[1]/v[2]/[3]/{id}"

Drag options to blanks, or click blank then click option'

Aapi

B1

Cusers

Dservice

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting versioning or using unclear resource names.

Using /api/v1/users/{id} clearly shows the API base, version, and resource, which helps usability and maintainability.

Practice

1. Why is consistent naming important in API design?

easy

A. It hides errors from users.

B. It makes the API run faster.

C. It reduces the size of the API code.

D. It helps developers understand and use the API easily.

Solution

1. Step 1: Understand the role of naming in APIs

   Consistent naming helps developers quickly recognize and remember API functions and parameters.

2. Step 2: Connect naming to usability

   When names are clear and consistent, developers spend less time guessing and more time building.

3. Final Answer:

   It helps developers understand and use the API easily. -> Option D

4. Quick Check:

   Consistent naming = easier API use [OK]

Hint: Good names make APIs easy to learn and use [OK]

Common Mistakes:

• Thinking naming affects speed
• Assuming naming reduces code size
• Believing naming hides errors

2. Which of the following is the correct way to define an API endpoint for getting user details?

easy

A. GET /user/details

B. FETCH userDetails()

C. POST /getUserDetails

D. DELETE /user/details

Solution

1. Step 1: Identify the HTTP method for retrieving data

   GET is the standard HTTP method used to retrieve data without side effects.

2. Step 2: Check the endpoint path format

   /user/details is a clear, RESTful path indicating user details resource.

3. Final Answer:

   GET /user/details -> Option A

4. Quick Check:

   GET method + clear path = correct API endpoint [OK]

Hint: Use GET for fetching data in REST APIs [OK]

Common Mistakes:

• Using POST to fetch data
• Using DELETE for retrieval
• Using non-HTTP syntax like FETCH

3. Consider this API response JSON for a user request:

{"id": 101, "name": "Alice", "email": "[e-mail]"}

What will the client see if the API changes the key email to user_email without updating the client code?

medium

A. The client will show an error or empty email field.

B. The client will show the email correctly.

C. The client will crash immediately.

D. The client will display the email under a different key automatically.

Solution

1. Step 1: Understand client-server data contract

   The client expects the key 'email' to exist in the response to display the email.

2. Step 2: Analyze effect of key name change

   Changing 'email' to 'user_email' breaks the expected key, so the client cannot find the email value.

3. Final Answer:

   The client will show an error or empty email field. -> Option A

4. Quick Check:

   Key name change without client update = missing data [OK]

Hint: Client expects exact keys; changes cause missing data [OK]

Common Mistakes:

• Assuming client auto-updates keys
• Thinking client crashes always
• Believing client shows old key data

4. An API returns error messages as plain text strings. Developers complain it's hard to handle errors. What is the best fix?

medium

A. Return errors as HTML pages.

B. Remove error messages to avoid confusion.

C. Return error messages as structured JSON with error codes.

D. Send errors only in HTTP headers.

Solution

1. Step 1: Identify the problem with plain text errors

   Plain text errors lack structure, making it hard for clients to parse and react programmatically.

2. Step 2: Choose a structured error format

   Structured JSON with error codes allows clients to detect error types and handle them properly.

3. Final Answer:

   Return error messages as structured JSON with error codes. -> Option C

4. Quick Check:

   Structured errors improve client handling [OK]

Hint: Use structured JSON errors for clear client handling [OK]

Common Mistakes:

• Removing errors hides problems
• Using HTML breaks API consistency
• Sending errors only in headers loses detail

5. You are designing an API for a large system used by many developers. Which design choice best improves system usability and scalability?

hard

A. Return all data in one response to reduce calls, ignoring pagination.

B. Use clear, consistent naming with versioning and detailed error messages.

C. Use short, cryptic names to reduce URL length and avoid versioning.

D. Avoid documenting the API to encourage exploration.

Solution

1. Step 1: Consider usability factors

   Clear naming and detailed errors help developers understand and fix issues quickly.

2. Step 2: Consider scalability factors

   Versioning allows safe API evolution; pagination avoids large responses that slow systems.

3. Step 3: Evaluate options

   This option combines best practices for usability and scalability; others harm either or both.

4. Final Answer:

   Use clear, consistent naming with versioning and detailed error messages. -> Option B

5. Quick Check:

   Clear naming + versioning + errors = best API design [OK]

Hint: Combine clarity, versioning, and errors for scalable APIs [OK]

Common Mistakes:

• Choosing cryptic names to save space
• Ignoring pagination causing slow responses
• Skipping documentation hurting usability