Remove repeated tariff parsing from the quote hot path
A CPU profile shows every quote parsing the same tariff document, including requests that use the same immutable tariff revision.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- CPU profiling · Cache invalidation
Estimated field mix
- Performance engineering70%
- Backend30%
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
- Parse once per tariff revision and cap retained revisions with an explicit eviction policy.
- Keep quote totals and rounding behavior identical to the uncached path for the seeded fixture.
- Reject a malformed new revision without replacing the last valid parsed tariff.
Implementation constraints
- Measure before and after with the same revision distribution; do not cache request-specific discounts in the shared tariff object.
Verification to include
- Compare every synthetic quote against the uncached implementation across two valid revisions.
- Alternate malformed and valid revisions, then force eviction and verify both bounded memory and correct reparsing.
Deliverables
- Profile comparison, bounded parsed-tariff cache and regression tests
Rollout and recovery
Gate parsed-tariff reuse behind a switch; reverting uses the original parser and discards only derived cache entries.
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.