Think Through Migrations & Evolution

Overview

Production guidance for changing running systems safely. Each reference paper captures the sequences that prevent outages: expand-and-contract instead of in-place renames, resumable backfills that do not overwrite newer writes, compatibility windows for old clients, CDC pipelines with reconciliation, and cutover plans with genuine rollback.

Core principle: A migration is a distributed system that runs while the old and new versions are both live. Every step must tolerate mixed versions, partial failure, and rollback — code rollback never undoes committed data.

Domain Law