Separate quote queue time from carrier lookup time
A trace labels the entire request as carrier latency, but the stub returns quickly when called outside the API.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Tracing · Queueing
Estimated field mix
- Performance engineering60%
- Site reliability40%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional freight broker sees slow quote responses at dispatch handover. The service looks healthy in average-latency charts, yet a few long requests occupy every worker. Build a small synthetic quote service and controlled dependency stub before taking implementation tickets.
Setup prerequisites
- Create a local quote endpoint and a deterministic carrier-price stub; no repository or dataset is supplied.
- Use synthetic routes and a fixed workload manifest. Record runtime, machine resources and instrumentation settings.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Record monotonic durations for admission wait, application work and carrier lookup with one request correlation identifier.
- Make the phase durations reconcile with total server duration within documented instrumentation overhead.
- Record cancellation and missing-span states explicitly instead of inventing zero-duration work.
Implementation constraints
- Do not put route payloads or credentials into spans; use a bounded synthetic request identifier for this exercise.
Verification to include
- Inject 100 ms of queue delay and verify it appears outside the carrier span.
- Cancel a queued request and confirm the trace distinguishes waiting from a lookup that never started.
Deliverables
- Span boundaries and an annotated trace from the controlled stub
Rollout and recovery
Enable sampling locally first; disable extra spans independently if instrumentation changes the measured workload.
Value of the work
For the engineer: Learn to distinguish queueing, dependency delay, CPU work and measurement mistakes using reproducible observations.
For the team: Produce a reviewable diagnosis and guarded changes that could guide a team investigating customer-visible latency.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.