What is a Trace?

The metric said something was slow.
The logs said something went wrong.
But neither could say where, or in what order.

incident report

Users report that checkout is slow.

You have metrics and logs from four services: gateway, api, orders, and database. Can you find the bottleneck?

metrics dashboard

842

requests / min

1.2s

latency p99

Request count looks normal. But latency is high.
The metric tells you something is slow — but not which service.

log viewer — last 5 seconds

14:32:01.204 [gateway] incoming POST /checkout

14:32:01.218 [api] validating cart items

14:32:01.307 [database] query inventory_check: OK

14:32:01.412 [orders] reserve_stock called

14:32:01.884 [database] write order_record: OK

14:32:02.003 [orders] confirmation generated

14:32:02.117 [api] response sent: 200 OK

14:32:02.130 [gateway] POST /checkout completed

From the metrics and logs alone, can you tell which service is causing the slowness?

following one request

gateway

→

api

→

orders

→

database

timing breakdown:

gateway

0 – 1200ms

api

14 – 950ms

orders

100 – 800ms

database

140 – 360ms

What you just did — following one request through multiple services — is called a...

trace

A trace follows a single request from beginning to end.

What metrics and logs could not reveal alone, the trace shows.