Capstone - The Zero-Downtime Migration

1. How This Capstone Works

The scariest changes in production are not features. They are migrations: changes to the shape of data. Here the data is being written 400 times a second by a system that must not stop. This capstone ships one migration, end to end, under the module's two laws. The first is the deploy/release split. The second is rollback as a routine act at every single step. That includes the steps where naive rollback is impossible. Those steps must be restructured until rollback is possible.