Incident Dossier

Failover Still Routes to Primary

A fictional notification service has primary and secondary provider regions. During a regional incident, health checks correctly mark the primary unhealthy and the secondary healthy, yet every delivery still targets the primary and fails. Trace the route-selection path and restore deterministic failover without duplicating delivery or hiding real errors.

Initial failing signalUnhealthy primary remains selectedExpected behavior: Delivery uses the healthy secondary region when the primary region is unhealthy · actual behavior: The router selects the unhealthy primary region and delivery throws primary region unavailable

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Compare the healthy-primary case with the unhealthy-primary case.
Trace how route health is read and how the delivery target is selected.
Make route selection honor health without retrying or duplicating the delivery operation.

Focus Mode

Start

src/delivery-router.js

Likely area

src/delivery-router.js
tests/delivery-router.test.mjs

Challenge Coach

Hints reveal broad direction first, then narrow toward the suspect path without showing hidden tests or exact solution code.

TopicReliability

DifficultyMedium

Est. time20 min

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Evidence Map

Failing signal loaded from challenge API
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workspace

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