Model recovery-point and recovery-time limits for a regional outage
A stakeholder asks for zero data loss and immediate recovery even when replication is asynchronous and the primary is unreachable.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Recovery objectives · Risk analysis
Estimated field mix
- Site reliability50%
- System design30%
- Distributed systems20%
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.
- AREGION-101 · Classify shipment reads by tolerated staleness
- AREGION-102 · Calculate regional latency contributions with stated assumptions
- AREGION-103 · Record the decision between regional caching and replica reads
- AREGION-104 · Define a read-after-write token for shipment changes
- AREGION-105 · Fence regional write authority before promoting a standby
- AREGION-106 · Preserve command identity across a regional routing retry
Acceptance criteria
- Define what RPO and RTO mean for the chosen workload.
- Calculate loss and recovery bounds from explicit lag and detection assumptions.
- Identify guarantees the design cannot currently provide.
Implementation constraints
- Use hypothetical numbers and separate targets from measured results.
Verification to include
- Calculate the declared outage scenario with bounded lag.
- Remove the lag bound and show that a finite loss guarantee is unsupported.
Deliverables
- Recovery objectives worksheet
Rollout and recovery
Review targets before infrastructure approval; revise guarantees when provider constraints differ.
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.