Protect customer-code renames during the backfill window
A rename races a batch lookup and attaches a legacy case to the wrong customer when the old code is reused.
- Focused work estimate
- 5h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Concurrency · Migration safety
Estimated field mix
- Database engineering80%
- Backend20%
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 support platform stores a mutable external account code as its primary relationship key. Renames and imports now break references in several tables.
Setup prerequisites
- Create a disposable database with synthetic customers and dependent records.
- Apply real migration files; never use production db push.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- AMIGRATE-101 · Inventory every reference to the mutable customer code
- AMIGRATE-102 · Add immutable customer IDs through an additive migration
- AMIGRATE-103 · Add nullable customer-ID references to dependent tables
- AMIGRATE-104 · Backfill customer IDs with resumable keyset batches
- AMIGRATE-105 · Bridge legacy customer writes to the new identity transactionally
Acceptance criteria
- Resolve against a stable captured mapping or guarded revision.
- Prevent ambiguous code reuse during transition.
- Keep committed references bound to immutable customer identity.
Implementation constraints
- Document the locking or mapping-version strategy.
Verification to include
- Race rename with backfill using two database clients.
- Reuse an old code after the allowed boundary and preserve earlier references.
Deliverables
- Rename/backfill concurrency guard
Rollout and recovery
Temporarily constrain code reuse under the migration policy; pause backfill on mapping conflicts.
Value of the work
For the engineer: Practice migration ordering, compatibility and referential integrity.
For the team: Review a reversible schema transition with measurable completeness checks.
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.