System design interviews — what good looks like
How strong candidates frame trade-offs under pressure.
The best system design candidates we see don't rush to a diagram. They spend the first five minutes negotiating the problem — clarifying scale, read/write ratios, consistency expectations, and what 'done' looks like for this interview.
Strong candidates name their trade-offs explicitly. 'I'm choosing eventual consistency here because the product can tolerate a 200ms staleness window, and it lets us scale reads horizontally' beats silently drawing a Cassandra cluster.
Weak signals: jumping straight to microservices, naming specific AWS products before naming the requirements, and treating the interview as a trivia round about CAP theorem.
Strong signals: drawing a single-box solution first and explaining why it would fail at the target scale, then introducing complexity one layer at a time. This shows judgment, not just knowledge.
If you're interviewing, practise out loud with a timer. The gap between 'I know this' and 'I can explain this in 45 minutes under pressure' is wider than most candidates think.