Database Migration Strategies That Avoid Downtime

The safest schema migrations are additive and backward compatible, adding new columns or tables without immediately removing old ones the running application still depends on.

A typical pattern is to deploy code that can handle both the old and new schema, migrate the data, then deploy a second release that removes support for the old structure.

We plan migrations in these stages by default for any client with meaningful production traffic, since a single big bang migration is where most downtime incidents come from.