Compare Latency Percentiles From Two Timing Samples

Tail Lens compares two lists of elapsed times measured in milliseconds. Paste a baseline and a new sample to inspect p50, p95 and p99 alongside mean and maximum timings. Percentiles use the nearest-rank method: sort the values and select the value at the ceiling of the percentile times sample count. This describes the pasted samples; it does not test statistical significance or control for different workloads.

How to use Tail Lens

1. Paste non-negative timing numbers for A and B, separated by commas, spaces or new lines; omit the ms unit.
2. Select Compare timings to see each sample's percentile values and B's percentage change from A. Lower milliseconds mean faster timing.
3. Inspect the slow tail and sample counts, then download the text report or change a sample and compare again. Small samples make p95 and p99 especially sensitive to single values.