Box plot · Diagram Design

Checkout's box is the incident

Five services, one shared latency axis from zero. Auth and Search keep a tight box under 40 ms. Checkout's box already runs 80–200 ms, and two requests sit past 380 ms — the median still looks survivable, which is exactly why the box is the reading that matters.

Checkout's box is the incident Horizontal box plots of per-request latency for five services on a shared linear axis from zero; Checkout's interquartile range runs from 80 to 200 ms with outliers at 388 and 396 ms. PER-REQUEST LATENCY, MS 0 100 200 300 400 Auth Catalog Checkout Search Billing LEGEND BOX = IQR · LINE = MEDIAN · DOT = OUTLIER Checkout · focal, the IQR that will page service · box is q1–q3, whisker to the last inlier

The box, not the middle

Checkout pages on the IQR

Checkout's median is 120 ms. Its box already spans 80–200 ms, and two outliers sit at 388 and 396 ms. A single average would have called this service healthy. The five-number summary is the incident.

One shared scale

Zero to 400 ms, linear

Every box, median, whisker and outlier sits on one linear axis from zero. Auth's entire box fits inside Checkout's lower whisker. That comparison is the point of putting five services on one figure.

Outliers stay outside

Dots past the fence

Whiskers run to the last inlier, not to the theoretical fence, and the two Checkout requests past its 380 ms fence keep their own marks. Drawing them on the whisker would have hidden the tail the title is about.

PER-REQUEST LATENCY · FIVE SERVICES · ILLUSTRATIVE FIGURES, NOT MEASURED TRAFFIC DIAGRAM DESIGN · BOX PLOT