Fundamentals
Latency
The time a single request takes end to end, normally reported as a percentile (p50, p95, p99) rather than an average.
Why interviewers ask about it
Always quote a percentile. On a page making 100 backend calls, about 63% of page loads hit at least one p99 - which is why tail latency, not the mean, is what users experience.
Related terms
This term is part of the free System Design interview preparation module - browse the full glossary for every definition.