Performance Baseline
A performance baseline is a recorded set of performance metrics — response times, throughput, resource usage — captured under known, controlled conditions, used as the reference point every future measurement gets compared against to detect improvement or regression.
Without a baseline, "is this fast" has no objective answer — a baseline turns performance testing from a one-off snapshot into an ongoing comparison, making it possible to say precisely "checkout is now 40% slower than it was after last week's release" rather than relying on a vague sense that things feel sluggish.
Baselines need to be re-established deliberately when the system's expected performance profile legitimately changes — a major feature addition, a significant traffic growth, a new infrastructure — otherwise a stale baseline either masks real regressions or flags legitimate, expected changes as false alarms.
