200-901 Understanding and Using APIs Practice Question
This 200-901 practice question tests your understanding of understanding and using apis. 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 developer receives HTTP 409 Conflict when updating a network configuration via Cisco NX-OS API. Which two scenarios could cause this error?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The resource was recently modified by another client.
HTTP 409 Conflict indicates a request conflicts with the current state of the resource. In the context of Cisco NX-OS API, this error occurs when the resource was recently modified by another client (option A) or when the update conflicts with a lock held by another transaction (option B). Both scenarios involve a state mismatch that the server cannot resolve without client intervention, often requiring the client to re-fetch the resource and retry.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The resource was recently modified by another client.
Why this is correct
A concurrent modification leads to a version conflict, resulting in 409.
Related concept
Read the scenario before looking for a memorised answer.
✓
The update conflicts with a lock held by another transaction.
Why this is correct
Locking conflicts cause a 409 Conflict error.
Related concept
Read the scenario before looking for a memorised answer.
✗
The request body contains malformed JSON.
Why it's wrong here
Malformed JSON results in a 400 Bad Request, not 409.
✗
The request includes unsupported parameters.
Why it's wrong here
Unsupported parameters typically cause a 400 Bad Request.
✗
The API key used is invalid.
Why it's wrong here
An invalid API key results in 401 Unauthorized.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between client-side errors (400, 401) and server-side state conflicts (409), so the trap here is confusing a malformed request or authentication failure with a resource state conflict.
Detailed technical explanation
How to think about this question
NX-OS uses RESTCONF or NX-API REST with optimistic locking via ETags or If-Match headers; a 409 can occur when the ETag provided does not match the current resource version. Under the hood, NX-OS may also enforce pessimistic locking through the Cisco NX-OS configuration session mechanism (e.g., 'configure terminal' exclusive lock), where another transaction holds a lock, causing a 409 on concurrent write attempts. In real-world scenarios, this is common in automation pipelines where multiple controllers attempt to modify the same interface or VLAN simultaneously.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Understanding and Using APIs — This question tests Understanding and Using APIs — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The resource was recently modified by another client. — HTTP 409 Conflict indicates a request conflicts with the current state of the resource. In the context of Cisco NX-OS API, this error occurs when the resource was recently modified by another client (option A) or when the update conflicts with a lock held by another transaction (option B). Both scenarios involve a state mismatch that the server cannot resolve without client intervention, often requiring the client to re-fetch the resource and retry.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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