Add immutable customer IDs through an additive migration
The migration needs stable customer identity while current clients continue using external codes.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Migrations · Database constraints
Estimated field mix
- Database engineering100%
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.
Acceptance criteria
- Add an opaque unique customer ID with a safe creation path.
- Keep legacy code uniqueness under its current scope.
- Do not remove or rename existing columns yet.
Implementation constraints
- Use a migration file and inspect generated SQL.
Verification to include
- Apply the migration to a populated synthetic database.
- Attempt duplicate immutable identity and verify a database rejection.
Deliverables
- Additive migration and schema assertions
Rollout and recovery
Apply to a disposable copy first; rollback additive consumers before considering column removal.
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.