standard

Expand/Contract Migration Pattern

A schema-change discipline that splits a breaking database change into an additive phase, a backfill with dual writes, and a removal phase, so old and new application versions can both run against one database.

Known aliases

expand and contract
parallel change

Relationships

No evidence-backed relationships are recorded.

Current clusters

build1 publisher

A single long SELECT stretches an instant ALTER TABLE into minutes of Postgres downtime

A dev.to field report traces migration outages to the order in which Postgres grants locks, and prescribes a lock_timeout of a few seconds plus a three-deploy expand, backfill and contract sequence for every breaking change.

Publishers:dev.to

Reality

Evidence68
Adoption: Insufficient
Hype gap+8
Incentives15
Confidence63