Traces

A trace answers one everyday question: how long did that take, and what happened along the way? When someone taps checkout in your app, a trace is the stopwatch that starts when the tap lands and stops when the order is confirmed — 480 ms later, say — noting each step in between.

Each timed step is called a span. A span has a name (checkout), a start and end time, and an optional parent, so a big operation can contain smaller ones — checkout wrapping charge card and reserve stock. Laid end to end, spans show you exactly where the time went, and when something is slow, which step to blame.

Record a span

You record spans through one combined entry point, WarpTelemetry. export() finishes the instant the span is safely on the device — it does not wait for a network.

val telemetry = WarpTelemetry(replica = ReplicaId("device-uuid-abc123"), store = InMemoryDurableStore())
telemetry.recover()   // bring back anything recorded before the app was last closed

telemetry.spans.export(span)   // one timed unit of work

Where they go

Recording is only the first step. Your spans are held safely on the device, survive being offline, and reach your dashboard with no duplicates — even carried off a phone by another device that happened to be online. That whole journey is on Device to dashboard.

Last modified: 02 July 2026