Blue-Green Database Migrations Without Downtime

Database changes are scary. The blue-green pattern adapted for databases lets you migrate without user impact.

Setup

Spin up new database (green) alongside old (blue).

Replicate from blue to green continuously.

The flip

Drain writes to blue (briefly).

Verify replication caught up.

Flip application config to green.

Resume writes.

Rollback

Reverse: replicate green back to blue. Flip back if needed.

Window of risk: between drain and flip. Keep it short.