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 is troubleshooting a Cisco RESTCONF API call that returns a 409 Conflict error. Which two scenarios could cause this? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The resource's current state conflicts with the requested change (e.g., trying to delete a resource that is in use).
Option B is correct because a 409 Conflict error in RESTCONF indicates that the request cannot be completed due to a conflict with the current state of the resource. For example, attempting to delete a resource that is referenced by other resources (e.g., a VLAN interface that is still active) violates the resource's state constraints, triggering this HTTP status code.
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.
✗
Authentication token is missing.
Why it's wrong here
Missing token results in 401 Unauthorized.
✓
The resource's current state conflicts with the requested change (e.g., trying to delete a resource that is in use).
Why this is correct
State conflicts, like deleting a resource that is referenced, cause 409.
Related concept
Read the scenario before looking for a memorised answer.
✓
The resource already exists and the request attempts to create a duplicate.
Why this is correct
Creating a duplicate resource is a typical cause of 409.
Related concept
Read the scenario before looking for a memorised answer.
✗
The resource does not exist.
Why it's wrong here
A missing resource would give 404, not 409.
✗
The request contains invalid data types.
Why it's wrong here
Invalid data types result in 400 Bad Request.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 409 Conflict and 400 Bad Request, where candidates mistakenly think invalid data types cause a conflict rather than a client-side syntax error.
Detailed technical explanation
How to think about this question
Under the hood, RESTCONF uses the HTTP 409 status code to signal a violation of YANG data model constraints, such as mandatory leaf presence, unique key violations, or referential integrity (e.g., a leafref pointing to a non-existent instance). In real-world scenarios, this often occurs when trying to create a resource with a duplicate key (e.g., two interfaces with the same name) or when a dependency prevents deletion (e.g., a BGP neighbor referencing a deleted route map).
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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's current state conflicts with the requested change (e.g., trying to delete a resource that is in use). — Option B is correct because a 409 Conflict error in RESTCONF indicates that the request cannot be completed due to a conflict with the current state of the resource. For example, attempting to delete a resource that is referenced by other resources (e.g., a VLAN interface that is still active) violates the resource's state constraints, triggering this HTTP status code.
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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