Google Professional Data Engineer Question 188
Single answerGoogle Cloud PlatformYou are designing a data pipeline to analyze user activity logs for a large e-commerce platform. The logs contain timestamps down to the millisecond level. The analysis team needs to generate hourly and daily aggregate reports on user activity, such as the number of purchases and page views. What is the most appropriate granularity for storing the timestamps in your data warehouse to optimize storage and query performance?
- A
Millisecond
- B
Second
- C
Minute
- D
Hour
Show answer and explanation
Correct answer: B
Explanation
The analysis team needs hourly and daily aggregate reports, so storing timestamps at the second granularity is optimal. This level of detail supports the required computations while avoiding unnecessary storage overhead caused by millisecond-level data. Choosing granularity that matches or slightly exceeds the requirements of the analysis ensures both performance and efficiency.
- A. Incorrect.
Millisecond granularity is unnecessary for the given use case as the analysis does not require such fine detail. Storing data at this level would waste storage and reduce query performance.
- B. Correct.
Second granularity is appropriate because it balances sufficient detail for analysis while avoiding excessive storage usage. It allows for efficient computation of both hourly and daily aggregates.
- C. Incorrect.
Minute granularity would result in a loss of detail that could be useful for future fine-grained analytics and does not significantly improve storage or query performance over seconds for this use case.
- D. Incorrect.
Hour granularity is too coarse for this use case, as it would make it impossible to perform detailed analysis or compute aggregates at a finer level of granularity.