PCDOE Practice Question: Applying site reliability engineering practices
A company uses Cloud Run for a stateless API service with concurrency set to 80. During a traffic spike, some requests return HTTP 500 errors and latency spikes. Cloud Monitoring shows container CPU utilization at 100% and memory usage at 70%. What is the most likely cause and the best first step?
⚠ Common exam trap
Google Cloud often tests the misconception that HTTP 500 errors during spikes are always due to insufficient instances or memory, but the key diagnostic clue here is CPU at 100% with memory well below limit, pointing to concurrency overload as the root cause.
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
✓
Concurrency per container is too high; reduce concurrency to 10
With CPU at 100% and memory at only 70%, the bottleneck is CPU, not memory. Cloud Run containers handle requests concurrently; setting concurrency to 80 means each container processes up to 80 requests simultaneously. When CPU is saturated, requests queue up, causing latency spikes and eventual HTTP 500 errors as the container becomes unresponsive. Reducing concurrency to 10 lowers the per-container request load, allowing each request to complete before CPU saturation occurs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Concurrency per container is too high; reduce concurrency to 10
Why this is correct
Lowering concurrency reduces CPU contention, preventing timeouts and 500s.
- ✗
Maximum instances limit is too low; increase from 10 to 100
Why it's wrong here
Cloud Run scales automatically; max instances limit prevents unbounded scaling but 500s indicate per-instance overload.
- ✗
Min idle instances is too low; set min idle to 5 to reduce cold starts
Why it's wrong here
Cold starts cause latency but not 500s; CPU is already 100%.
- ✗
Memory limit is too low; increase memory from 256 MiB to 512 MiB
Why it's wrong here
Memory usage is only 70%, so memory is not the bottleneck.
Go deeper
Related to this question
About these practice questions
Courseiva writes every PCDOE question from scratch — 486 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDOE 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 PCDOE exam.