Backend & systems·Observability and operations
you keep one percent of traces because storing all of them costs more than the service does.
Trace sampling
Also calledhead sampling, tail sampling
Recording only a subset of traces to bound cost. Head sampling decides at the start and is cheap but blind; tail sampling decides after seeing the whole trace and can keep all the errors and slow ones, at the cost of buffering. Uniform head sampling is why the trace for the incident you care about is usually missing.