DP-203 Develop data processing Practice Question
Your team is developing a real-time data processing solution using Azure Stream Analytics. The input is from Azure Event Hubs. The output must be written to Azure SQL Database. You need to ensure that the processing guarantees exactly-once semantics for the output. Which output configuration should you use?
⚠ Common exam trap
A common mix-up: candidates confuse 'Exactly once' with 'At least once', assuming that 'At least once' is sufficient for guaranteed delivery, but they overlook that 'At least once' can produce duplicates, which violates exactly-once requirements.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set output mode to 'Exactly once'
Azure Stream Analytics supports exactly-once semantics for output to Azure SQL Database when the output mode is set to 'Exactly once'. This ensures that each event is processed and written exactly once, preventing duplicates even in the event of failures or retries. The 'Exactly once' mode uses internal checkpointing and transactional writes to guarantee this behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set output mode to 'When possible'
Why it's wrong here
Invalid output mode.
- ✓
Set output mode to 'Exactly once'
Why this is correct
Ensures no duplicate writes to SQL Database.
- ✗
Set output mode to 'At least once'
Why it's wrong here
At least once can produce duplicates.
- ✗
Set output mode to 'Best effort'
Why it's wrong here
Invalid output mode.
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Written by Johnson Ajibi, MSc IT Security
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