200-901 Software Development and Design Practice Question
This 200-901 practice question tests your understanding of software development and design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A REST API returns a 500 Internal Server Error when a client sends a malformed JSON payload. What is the most appropriate HTTP response code to indicate a client-side error?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
400 Bad Request
Option A is correct because 400 Bad Request is used when the server cannot process the request due to client error (e.g., malformed syntax). Option B (401) is for authentication failures. Option C (403) is for authorization failures. Option D (422) is for unprocessable entities when the syntax is correct but semantics fail. Therefore, 400 is the best choice for a malformed JSON payload.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
400 Bad Request
Why this is correct
400 indicates the server cannot process the request due to malformed syntax, which fits a malformed JSON payload.
Related concept
Authentication checks who the user is.
✗
401 Unauthorized
Why it's wrong here
401 is used when authentication is required and has failed or not been provided.
✗
403 Forbidden
Why it's wrong here
403 indicates the server understood the request but refuses to authorize it.
✗
422 Unprocessable Entity
Why it's wrong here
422 is for well-formed requests that contain semantic errors, not for malformed syntax.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 200-901 questions on access control and AAA configuration.
Software Development and Design — This question tests Software Development and Design — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: 400 Bad Request — Option A is correct because 400 Bad Request is used when the server cannot process the request due to client error (e.g., malformed syntax). Option B (401) is for authentication failures. Option C (403) is for authorization failures. Option D (422) is for unprocessable entities when the syntax is correct but semantics fail. Therefore, 400 is the best choice for a malformed JSON payload.
What should I do if I get this 200-901 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 200-901 questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
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Question Discussion
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