Backend & systems·Deployment, release and rollback
you add the new column, write to both, backfill, switch reads, and only remove the old one in a later deploy.
Expand and contract
Also calledparallel change, expand-migrate-contract
The multi-step pattern for making a breaking change safely: expand the schema or contract additively, migrate over, then contract by removing the old form once nothing uses it. Each step is independently deployable and reversible. It takes three deploys instead of one, which is the price of never having a window where old and new code cannot coexist.