LESSON 4.2
Schema migrations without downtime
Learn key techniques and workflows in PostgreSQL for Developers.
31m
intermediate
5,747 students
Overview
A migration runs against a live application. Expand, migrate, contract lets you change a schema while both old and new code are running.
In this lesson you will:
- Apply the expand, migrate, contract pattern
- Avoid locks that block writes on large tables
- Make every migration reversible or forward-only on purpose
Pro Tip
Use caching and revalidation wisely to ensure your app stays fast and data remains fresh without unnecessary requests.