[DEE-300] Schema Evolution Overview

This DEE is a category overview for Schema Evolution principles.

Database schemas are not static. As applications grow, requirements change, and teams learn more about their domain, the schema must evolve. Schema evolution encompasses the practices, patterns, and tools that allow teams to change database structure safely, without downtime, and without breaking running applications.

The principles in this category cover the full lifecycle of schema changes: how to capture them as versioned migrations, how to ensure backward compatibility during rolling deployments, how to avoid locking production tables, how to backfill data efficiently, and how to track which changes have been applied.

Related DEEs

• DEE-301 Migration Fundamentals -- versioning schema changes like code
• DEE-302 Backward-Compatible Schema Changes -- the expand-and-contract pattern
• DEE-303 Zero-Downtime Migrations -- avoiding locks during schema changes
• DEE-304 Data Backfilling Strategies -- batched updates for existing rows
• DEE-305 Schema Versioning -- tracking migration state in the database