PCDE Monitor and optimize database performance Practice Question
You are running a production workload on Cloud Bigtable and notice that read latency has increased. Upon reviewing the monitoring dashboard, you see that CPU utilization is below 50% but the number of active tablets is high. What is the most likely cause of the increased read latency?
⚠ Common exam trap
Google Cloud often tests the misconception that high tablet count is always beneficial for parallelism, when in fact it can degrade performance due to metadata overhead, especially when CPU is not the bottleneck.
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
✓
There are too many tablets, causing increased metadata operations and slower reads.
In Cloud Bigtable, each tablet is a contiguous range of rows managed by a tablet server. When the number of active tablets is high, the tablet server must perform more metadata operations (e.g., splitting, merging, and serving multiple tablets) which increases per-request overhead and can degrade read latency. This is true even when CPU utilization is below 50%, because the overhead is not purely CPU-bound but involves increased I/O and coordination.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Read requests are being throttled due to exceeding IOPS limits.
Why it's wrong here
Throttling would increase CPU, but CPU is low.
- ✓
There are too many tablets, causing increased metadata operations and slower reads.
Why this is correct
Excessive tablets increase the overhead of metadata lookups and tablet splitting, leading to higher latency.
- ✗
A hot node is throttling read requests.
Why it's wrong here
CPU utilization is below 50%, so a hot node is unlikely.
- ✗
The cluster is underprovisioned, causing resource contention.
Why it's wrong here
Underprovisioning would cause high CPU, not low CPU.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud 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 PCDE exam.