Define a read-after-write token for shipment changes
A user changes a delivery note, then a regional read immediately shows the previous text.
- Focused work estimate
- 3h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Read-your-writes · Routing
Estimated field mix
- Distributed systems60%
- System design40%
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 logistics dashboard serves distant customers from one primary region. Stakeholders want faster reads and outage recovery but have not agreed which data may be stale.
Setup prerequisites
- Create a local primary/replica simulator and synthetic shipment records.
- Use local models; no multi-region infrastructure is provisioned.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Mutation returns an accepted version token.
- A subsequent read must meet that version or use a fresh source.
- Tokens are bound to tenant and resource.
Implementation constraints
- Implement a small local routing model, not a new replication engine.
Verification to include
- Write version 4 while the replica has version 3 and route correctly.
- Reuse another tenant's token and reject it without exposing state.
Deliverables
- Read-version contract and routing tests
Rollout and recovery
Canary the routing model in a local client; fall back to primary reads when freshness cannot be established.
Value of the work
For the engineer: Practice consistency tradeoffs, failover authority and recovery assumptions.
For the team: Review regional availability proposals with explicit data-loss and staleness limits.
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.