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World O4: The Diary & One Order

Traces and spans

You will learn: to read one order as a trace made of spans, and see which step was slow.

Checked with Prometheus 3 on 1 Nov 2026

The problem

Order A1043 took almost 2 seconds. It passed through kedai-api and kedai-pay. Which step ate the time?

Watch

Tap each point on the timeline.

A trace is the whole order. Each step is a span: One step of an order, with a start and an end time. Spans nest: a parent span holds child spans., with a start and an end. Tap through it.

Watch

This is the real Collector's debug output for that order. Tap the line that links the child to its parent.

0 of 1 found

Both spans share one trace ID: The order number every span and log line of one request shares: 32 hex characters.: the order number.

Predict

pay card took 1.8 of the 1.95 seconds. Where do you look next?

Check

Drag a card into a box. Or tap the card, then tap the box.

      The real output said Kind: Server and Kind: Client. Sort these spans.

      You did it!

      You can now read a trace and find the slow span.

      Go deeper (optional)

      Spans also carry attributes (http.route: /order), events, and a status. A failed step sets the status to Error. Real rep: the official OpenTelemetry Demo runs a whole online shop on your laptop. See opentelemetry.io/docs/demo.