Quick Answer
The most likely cause of a spike in 429 errors is that your application is exceeding the transactions-per-second (TPS) limit for your Azure AI Vision pricing tier. This error is Azure’s standard rate-limiting response, designed to protect backend resources by throttling clients that send requests faster than the service can handle. On the Microsoft Azure AI Engineer Associate AI-102 exam, this scenario tests your understanding of how Azure AI Vision enforces quotas and how to interpret HTTP status codes in production monitoring. A common trap is confusing 429 errors with authentication failures (401) or resource exhaustion (503); remember that 429 specifically signals you are sending too many requests too quickly. To avoid this, always check your TPS allocation against your usage metrics in Azure Monitor. Memory tip: think “429 = Too Fast, Too Furious” — your app is speeding past the tier’s speed limit.
This AI-102 practice question tests your understanding of plan and manage an azure ai solution. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Your company uses Azure AI Vision to analyze images. You receive an alert that the number of 429 (Too Many Requests) errors has increased significantly. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The endpoint URL is incorrect.
Why wrong: Incorrect endpoints cause 404 errors.
The API key has expired.
Why wrong: Expired keys cause authentication errors (401/403), not 429.
The service principal does not have the correct role assignment.
Why wrong: Insufficient permissions cause 403 errors.
The application is exceeding the transactions-per-second (TPS) limit.
429 errors occur when the request rate exceeds the allowed TPS.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The application is exceeding the transactions-per-second (TPS) limit.
HTTP 429 (Too Many Requests) is a rate-limiting response from Azure AI Vision when the client exceeds the allowed transactions-per-second (TPS) for the chosen pricing tier. The alert indicates the application is sending requests faster than the service's capacity, triggering throttling to protect backend resources.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The endpoint URL is incorrect.
Why it's wrong here
Incorrect endpoints cause 404 errors.
The API key has expired.
Why it's wrong here
Expired keys cause authentication errors (401/403), not 429.
The service principal does not have the correct role assignment.
Why it's wrong here
Insufficient permissions cause 403 errors.
The application is exceeding the transactions-per-second (TPS) limit.
Why this is correct
429 errors occur when the request rate exceeds the allowed TPS.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is confusing HTTP 429 with authentication or authorization errors (401/403), leading candidates to incorrectly select options about API keys or role assignments when the real issue is rate limiting.
Detailed technical explanation
Azure AI Vision enforces TPS limits per pricing tier (e.g., Free tier: 20 requests per minute, Standard tier: 10 TPS by default, adjustable via support). The 429 response includes a Retry-After header specifying the wait time in seconds. Under the hood, the service uses a token bucket algorithm to meter requests; exceeding the bucket capacity triggers throttling.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
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FAQ
Plan and manage an Azure AI solution — This question tests Plan and manage an Azure AI solution — Read the scenario before looking for a memorised answer..
The correct answer is: The application is exceeding the transactions-per-second (TPS) limit. — HTTP 429 (Too Many Requests) is a rate-limiting response from Azure AI Vision when the client exceeds the allowed transactions-per-second (TPS) for the chosen pricing tier. The alert indicates the application is sending requests faster than the service's capacity, triggering throttling to protect backend resources.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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