Debug and mitigate a CPU spike incident
Company: Discord
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: medium
Interview Round: Onsite
## Production Debugging: CPU Spike Incident (Open-Ended)
You are on-call for a backend service. An alert fires: **CPU usage suddenly spikes** on the service’s hosts/pods and stays high.
You can ask for any information you want (dashboards, time series metrics, logs, traces, recent deploys, config changes). The interviewer will provide whatever graphs/logs you request.
### Tasks
1. **Immediate mitigation:** What do you do first to reduce user impact?
2. **Triage plan:** What key questions do you ask and what metrics/logs do you inspect?
3. **Root cause analysis:** Walk through how you narrow down hypotheses to a likely root cause.
4. **Fix + verification:** How do you validate the fix and prevent regression?
Assume this is a typical microservice environment (Kubernetes or VM autoscaling, load balancer, centralized logging/metrics).
Overview: This question evaluates on-call incident response skills, focusing on production debugging, CPU spike mitigation, root-cause analysis, and verification in a microservice environment and is categorized under software engineering fundamentals.
Read the full Discord Software Engineer interview experience this question came from