Test old and new application queries during expand-contract changes
An application rollback fails because the migration removed the column the previous build reads.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Schema evolution · Compatibility
Estimated field mix
- Database engineering50%
- Quality engineering30%
- Developer tooling20%
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 subscription service has accumulated migration scripts with unclear lock risks and no consistent rehearsal output.
Setup prerequisites
- Create a disposable local database with synthetic subscriptions and a separate scratch database; author all fixtures locally.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Define old and new query fixtures.
- Run both after the expansion migration.
- Reject contraction while the old-query support window is open.
Implementation constraints
- Limit scope to one renamed subscription column.
Verification to include
- Verify dual compatibility after expansion.
- Demonstrate the old query failing after premature contraction.
Deliverables
- Compatibility rehearsal.
Rollout and recovery
Ship expansion first; delay contraction until the documented rollback window closes.
Value of the work
For the engineer: Practice migration tooling, lock reasoning, and clear developer feedback.
For the team: Provide reviewers with repeatable migration checks and explicit recovery 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.