The order total from the other regionCaching & StateHardPreparing

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Incident Dossier

The order total from the other region

Support reports that an order lookup occasionally shows the total and currency for a different regional storefront. The database records are correct, and the request handler logs the right tenant. Trace the read path across the HTTP, service, cache, and repository layers before changing the smallest safe boundary.

Initial failing signalRegional order lookup returns the wrong currencyExpected behavior: Each tenant receives its own order snapshot. · actual behavior: The second tenant can receive the first tenant's cached snapshot.

Codebase incident

Evidence desk

Harbor Commerce · 1

At 14:07 UTC, support reports an order total rendered in USD for a customer in the EU storefront. The issue is intermittent and appeared after the flash-sale traffic increase. A direct repository read is correct; only repeated reads through the API are suspect.

Customer symptom

A customer sees another regional storefront's currency and total for an order lookup.

Expected

A cache hit is valid only for the same tenant and order id.

Actual

The cache can reuse a snapshot across tenants when the order id matches.

Architecture

HTTP controllerOrder serviceOrder cacheOrder repositoryPostgreSQL

HTTP controller → Order service · tenant + order id
Order service → Order cache · read-through
Order cache → Order repository · miss
Order repository → PostgreSQL · tenant-scoped query

Logs2

Request correlation

request=eu-17 tenant=eu-west order=ord-42 cache=hit currency=USD

orders.read

Direct repository comparison

tenant=eu-west order=ord-42 currency=EUR; tenant=us-east order=ord-42 currency=USD

orders.repository

Metrics1

Cache hit ratio

93% during the incident window; no database error spike observed

orders.cache.hit_ratio

Recent changes

Flash-sale traffic increased reads across regional storefronts.
The repository query already includes tenant isolation.
The cache was introduced to reduce repeated order reads.

Plausible hypotheses

Repository query loses tenant scope — The symptom crosses regional data boundaries, so the read boundary must be checked.
Cache identity is incomplete — The issue appears after repeated reads and the same order id exists in more than one region.
Currency formatting uses stale configuration — The visible difference is currency, which can be caused by a presentation or configuration layer.

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Read ord-42 for the us-east tenant.
Read the same order id for eu-west without resetting the process.
Compare the cached response with the repository response.
Trace the identity used by the read-through cache before editing.

Focus Mode

Follow the tenant and order id from the controller to the cache, then compare the cache key with the repository query.

Start

README.md
src/http/controller.js
src/cache/order-cache.js

Likely area

src/cache/order-cache.js
src/orders/service.js
src/orders/repository.js

Investigation path

1Confirm the symptom with the supplied test.
2Trace tenant identity through the controller and service.
3Compare cache identity with the repository's tenant-scoped lookup.
4Apply the narrowest fix and rerun visible and hidden checks.

Repo scale

17 meaningful files
HTTP, service, cache, repository, worker, and deployment context
One narrow cache-identity fix

Challenge Coach

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

TopicCaching & State

DifficultyHard

Est. time35 min

Workspacepreparing

Explorer

Loading files

Evidence Map

Failing signal loaded from challenge API
Workspace files loaded from workspace API
Results rendered only after API run/submit

Autosaved

workspace

Outputread-onlyready$ prepare workspace

Preparing workspace