I started at the client layer and worked my way down, which felt logical at the time but I think I skipped over some obvious stuff like DNS and CDN failures too quickly.
Start by clarifying the scope of the connection issue (e.g., specific user, region, or feature) and then systematically narrow down the root cause using a layered approach: client-side, network, server-side, and dependencies. Emphasize a data-driven methodology, leveraging metrics, logs, and tracing to isolate the problem, and propose both immediate mitigation and long-term fixes.
Pro tip: Demonstrate familiarity with Meta's scale by mentioning specific tools like Scuba, Dyno, or Canary, and highlight the importance of considering both technical and product metrics (e.g., user engagement drop) to prioritize the investigation.
Ask questions to understand the symptoms: Is it affecting all users or a subset? Which platform (iOS, Android, web)? When did it start? This helps define the problem boundaries and prioritize investigation.
Verify if the issue is isolated to the client (app version, device) or network (ISP, region). Use client logs, error rates, and network diagnostics to rule out local problems.
Inspect server health: error rates, latency, throughput, and resource utilization. Look for anomalies in service dependencies (e.g., databases, caches) and correlate with recent deployments or config changes.
Use distributed tracing to follow a request path and identify where failures occur. Check for timeouts, connection pool exhaustion, or misconfigurations in load balancers, DNS, or firewalls.
Propose immediate fixes (e.g., rollback, scaling, failover) and long-term solutions (e.g., improved monitoring, circuit breakers, chaos testing). Document findings and update runbooks.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.