Work out sli measurement window instantly with clear inputs, formula shown and shareable results.
An SLI window must contain enough failure events for the measured ratio to mean anything. At 150 requests per second and a 0.1 percent target failure rate, only 0.15 failures occur per second, so a five-minute window sees about 45 — workable, but halve the traffic and the same window becomes noise. Low-traffic services need long windows or count-based rather than ratio-based SLIs.
Window sizing
expected events = rate x failure rate x window seconds; minimum window = events needed / (rate x failure rate)
Use longer windows, aggregate across similar endpoints, or switch to synthetic probes that generate a known, steady request rate.
A short window catches fast burns quickly while a long window suppresses noise. Combining both with different burn-rate thresholds gives fast detection without constant false pages.