Google PCA Practice Question: Analysing and Optimising Technical and Business Processes
An application uses Cloud Bigtable and experiences high latency for reads. The row key is a timestamp prefix followed by a random ID. Queries often scan a range of timestamps for a specific ID. What design change would MOST improve read performance?
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
✓
Change the row key to start with the random ID followed by timestamp
For Bigtable, row key design is critical. Scanning a range of timestamps for a specific ID is inefficient if the key starts with timestamp (scans across all IDs). Prepending the ID ensures all data for that ID is contiguous, making range scans efficient. Adding nodes increases throughput but doesn't fix the key design issue. Using a column family is about grouping columns, not performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Change the row key to start with the random ID followed by timestamp
Why this is correct
This ensures rows for the same ID are clustered together, making timestamp range scans for a specific ID fast.
- ✗
Add more Bigtable nodes
Why it's wrong here
Adding nodes increases throughput but does not improve the latency of individual reads caused by poor row key design.
- ✗
Use a separate column family for the ID
Why it's wrong here
Column families are for grouping columns; they don't affect row key scanning performance.
- ✗
Enable Bigtable replication
Why it's wrong here
Replication improves availability and read throughput but does not fix the row key design issue affecting scan performance.
Go deeper
Related to this question
Learn chapter
Introduction to Google Cloud Platform
Key term
IDS
An IDS is a security system that monitors network or system traffic for suspicious activity and alerts administrators to potential threats, but does not actively block them.
Key term
Bigtable
Bigtable is Google's fully managed, scalable NoSQL database service designed for large analytical and operational workloads, handling petabytes of data with low latency.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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