16Write SQL for a cohort retention analysis (what % of users return in week N after signup).▼hardMetaAmazonNetflix2 replies○ sign inThe classic product-analytics SQL question. The signal is grouping users by signup cohort, deriving each activity's period offset, and counting distinct returners per offset to build the retention triangle.Open full answer →
102Design a time-series database that ingests millions of metrics per second and answers range queries fast.▼hardAmazonNetflixMicrosoft1 replies◆ premiumMetrics, traces, and IoT data are append-heavy, time-ordered, and seldom updated. A general database handles this poorly. The wins come from columnar layout, compression tuned for timestamps, downsampling, and retention. Here is the time-series design interviewers want.Open full answer →
52A key customer is about to churn. Walk me through how you would try to save the account.▼hardSalesforceDatabricksSnowflake2 replies◆ premiumRescuing a churning account is diagnosis under pressure: find the real reason, fix what you can, and win back trust with action. Interviewers look for a method, not a discount. Here is the move.Open full answer →
