Q: “Tell me about a time you improved system reliability”
“I participated in chaos engineering drills where we deliberately failed infrastructure components. We discovered that while graceful shutdowns had zero impact, ungraceful failures like machine reboots caused 10-30 second outages. This revealed our load balancer health checks were too slow.
I proposed reducing the health check interval and implementing connection draining timeouts. We validated this would have prevented the outages by simulating network failures with
tccommand in our staging environment before rolling to production.”
Q: “How do you validate your monitoring is effective?”
“Through fault injection testing. At HoYoverse, we used
tcto simulate 50% packet loss and 1-second latency increases while validating our Prometheus alerts triggered correctly. We tested that ourincrease(ping_failure_total[5m]) > 0alert caught network issues and our latency threshold of >300ms was appropriate given our baseline of 100-200ms cross-region.”
Points to explore: The unexpected failure
Observation: 10-30s request failure during machine down / restart; different from the proposal
Hypothesis 1: Connection pool poisoning
- Dead connections stayed in the pool
- When network recovered, app tried to reuse dead connections
- Had to fail once to realize connections were stale
Hypothesis 2: Load balancer state sync delay
- Health checks passed
- But load balancer routing tables not updated yet
- Sent traffic to instance not fully recovered
— Ask “Did we figure out why recovery also caused failures?”