Quick Answer
The answer is to make the function idempotent. This is correct because under high load, Event Hubs uses at-least-once delivery semantics, meaning the same event can be triggered multiple times; an idempotent Azure Function ensures that repeated processing of the same event produces the same result, effectively achieving exactly-once processing without losing events. On the AZ-204 exam, this concept tests your understanding of how to handle distributed system failures and retries—a common trap is to assume you can rely on the trigger itself for deduplication, but Event Hubs does not guarantee that. Instead, you must design your function to be safe to repeat, often by using a unique event identifier to check if processing already occurred. A helpful memory tip: think “IDEM” for IDEMpotent—if the input is the same, the output stays the same, no matter how many times you run it.
This AZ-204 practice question tests your understanding of develop azure compute solutions. 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 Azure Function app uses an Event Hub trigger. Under high load, some events are processed multiple times. You need to ensure exactly-once processing without losing events. What should you implement?
Make the function idempotent
Idempotent processing ensures same event handled once.
Use Azure Queue Storage instead
Why wrong: Doesn't solve the duplication issue inherently.
Enable checkpointing
Why wrong: Checkpointing helps with recovery, not deduplication.
Increase the batch size
Why wrong: Doesn't prevent duplicates.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Make the function idempotent
Option A is correct because making the function idempotent ensures that even if the Event Hub trigger delivers the same event multiple times (which can happen under high load due to at-least-once delivery semantics), the function's side effects are safe to repeat. Idempotency is the only reliable way to achieve exactly-once processing in a distributed system where the trigger itself does not guarantee deduplication.
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.
Make the function idempotent
Why this is correct
Idempotent processing ensures same event handled once.
Related concept
Read the scenario before looking for a memorised answer.
Use Azure Queue Storage instead
Why it's wrong here
Doesn't solve the duplication issue inherently.
Enable checkpointing
Why it's wrong here
Checkpointing helps with recovery, not deduplication.
Increase the batch size
Why it's wrong here
Doesn't prevent duplicates.
Common exam traps
The trap here is that candidates confuse checkpointing with deduplication, assuming it guarantees exactly-once processing, when in reality checkpointing only tracks read progress and does not prevent duplicate event delivery within the same batch or across restarts.
Detailed technical explanation
Event Hubs uses an at-least-once delivery model; under high load, the same event can be received by the trigger multiple times due to checkpoint failures, receiver rebalancing, or transient errors. Idempotent processing typically involves using a unique event identifier (e.g., the Offset or SequenceNumber) to detect and skip duplicates, often via a transactional store like Cosmos DB or Azure SQL with upsert logic. This pattern is critical in event-driven architectures where downstream systems cannot tolerate duplicate records.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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FAQ
Develop Azure compute solutions — This question tests Develop Azure compute solutions — Read the scenario before looking for a memorised answer..
The correct answer is: Make the function idempotent — Option A is correct because making the function idempotent ensures that even if the Event Hub trigger delivers the same event multiple times (which can happen under high load due to at-least-once delivery semantics), the function's side effects are safe to repeat. Idempotency is the only reliable way to achieve exactly-once processing in a distributed system where the trigger itself does not guarantee deduplication.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This AZ-204 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-204 exam.
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