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PLATENCY-108 · Protect the improvement

Choose an overload policy from the quote deadline budget

Practice briefTaskExpert

At overload, a larger queue increases completed work but most quotes arrive after the dispatch screen has already given up.

Focused work estimate
6h + prerequisites
Priority in the scenario
High
Engineering practice
Capacity planning · Tail latency · Load testing

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

  • Compare at least two admission policies at 0.5, 1.0 and 1.5 times the measured sustainable arrival rate.
  • Evaluate deadline success rate, rejection rate, p99 and queue depth together; document the selected tradeoff.
  • Implement the selected bounded policy and retain exact pricing correctness for every admitted request.

Implementation constraints

  • Use an open-loop arrival schedule and account for generator saturation; define sustainable rate from the recorded local baseline, not a guessed production number.

Verification to include

  • Run three repetitions per load level after fixed warmup and publish spread, request counts and all timeout outcomes.
  • Inject a carrier slowdown midway through a run and show queue depth remains bounded and recovery does not require restart.

Deliverables

  • Admission decision record, load results and overload recovery regression

Rollout and recovery

Canary against the declared deadline-success guardrail; revert policy configuration if correctness or rejection behavior differs from the approved contract.

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.