The answer is high CPU utilization on the cluster, specifically at 85%, which is the most likely cause of replication latency. This occurs because distributed database replication protocols like Raft or Paxos are inherently CPU-intensive, requiring frequent serialization, checksumming, and consensus processing; when CPU resources are saturated, the cluster cannot handle these replication requests in a timely manner, directly increasing latency. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of how resource contention impacts database performance, often appearing as a troubleshooting question where you must differentiate between network issues and compute bottlenecks. A common trap is to blame network bandwidth or disk I/O first, but remember that replication latency caused by high CPU utilization is a classic sign of a compute-bound process. Memory tip: think of replication as a CPU-hungry task—if the processor is nearly full, replication must wait in line.
PCDE Monitor and optimize database performance Practice Question
This PCDE practice question tests your understanding of monitor and optimize database performance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
```
# Bigtable cluster metrics
Cluster: my-cluster
Table: events
CPU utilization: 85%
Storage utilization: 70%
Replication latency (average): 15ms
Current nodes: 30
Recommended nodes: 25
Table load: uniform
```
Refer to the exhibit. You notice replication latency is 15ms. What is the most likely cause of this latency?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
High CPU utilization (85%) on the cluster
High CPU utilization (85%) on the cluster is the most likely cause of replication latency because the replication process (often using protocols like Raft or Paxos in distributed databases) is CPU-intensive. When CPU resources are saturated, the cluster cannot process replication requests in a timely manner, leading to increased latency. In many distributed database systems, replication involves serialization, checksumming, and network I/O, all of which compete for CPU cycles.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The table load is not uniform
Why it's wrong here
The exhibit says load is uniform.
✗
Storage utilization is at 70%
Why it's wrong here
70% is within acceptable limits.
✓
High CPU utilization (85%) on the cluster
Why this is correct
High CPU can slow down replication operations.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The number of nodes is above the recommended count
Why it's wrong here
More nodes usually reduce latency, not increase.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that storage utilization or node count are the primary causes of replication latency, when in fact CPU saturation is the most direct bottleneck for the replication protocol's processing pipeline.
Detailed technical explanation
How to think about this question
In distributed databases like CockroachDB or TiDB, replication latency is measured as the time between a write being committed on the leader and being acknowledged by a majority of replicas. When CPU utilization is high, the Raft consensus algorithm's heartbeat and log replication intervals can be delayed because the leader's CPU is busy handling other tasks, causing followers to miss heartbeats and trigger leader elections or slow down log appending. A real-world scenario is a cluster running heavy analytical queries that starve the replication goroutines, leading to increased p99 latency for writes.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Monitor and optimize database performance — This question tests Monitor and optimize database performance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: High CPU utilization (85%) on the cluster — High CPU utilization (85%) on the cluster is the most likely cause of replication latency because the replication process (often using protocols like Raft or Paxos in distributed databases) is CPU-intensive. When CPU resources are saturated, the cluster cannot process replication requests in a timely manner, leading to increased latency. In many distributed database systems, replication involves serialization, checksumming, and network I/O, all of which compete for CPU cycles.
What should I do if I get this PCDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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