Topic

Expand-migrate-contract

Schema change sequence that first adds new structures, then runs old and new read and write paths side by side, and only removes the old ones once the overlap period is judged safe.

Current clusters

build1 publisher

A migration canary can gate a column drop only if it reads rows it did not write

The expand-migrate-contract gate is only as strong as the rows the canary inspects. The sample worker in a dev.to write-up inserts its own test users and reads them straight back, and production row sampling is listed as a later addition.

Publishers:dev.to

Reality

Evidence52
Adoption: Insufficient
Hype gap+38
Incentives22
Confidence63