Stop expired quotes from holding carrier connections

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.

• PLATENCY-101 · Write down the traffic mix before comparing quote timings
• PLATENCY-102 · Show quote latency percentiles alongside rejected and timed-out requests
• PLATENCY-103 · Separate quote queue time from carrier lookup time

Acceptance criteria

• Propagate the remaining deadline through queue admission and the carrier client.
• Release the connection and remove queued work when the request is cancelled, including cancellation before dispatch.
• Return one bounded timeout outcome without automatically retrying a request whose caller has left.

Implementation constraints

• Use the stub to control headers, body completion and connection close separately; wall-clock sleeps alone do not prove cleanup.

Verification to include

• Cancel before dispatch, while waiting for headers and during a streamed response; count active work returning to baseline.
• Race normal completion against cancellation and confirm one response classification and no unhandled rejection.

Deliverables

• Deadline propagation and deterministic cancellation tests

Rollout and recovery

Canary the deadline path with active-connection counters; restore the previous client only after pending work drains.

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.