Always include a correlation ID that threads through every service in a request chain. Without it, debugging a distributed system is like searching for a needle in a hayfield, not just a haystack.
Strong answers cover: structured logging (JSON), correlation IDs across services, log levels used consistently, centralised aggregation, retention policies, and the balance between logging enough to debug and not so much that costs and noise become problems. Best candidates discuss how they make logs searchable and actionable during incidents.
Practical observability skill. Logs are the first tool engineers reach for during incidents. Candidates who have designed logging strategies for distributed systems understand observability at a deep level.