Every SaaS starts the same way. One database, every customer inside it, a tenant_id column keeping them apart. It's the default because it's easy, and for a long time, easy was enough.

It isn't anymore.

Your customers share one engine, so one customer's spike becomes everyone's slowdown.

Your customers share backups and indexes, so truly deleting one of them is archaeology.

Your customers share one location, so you can't promise anyone where their data lives.

And the day one customer demands their own database, you inherit an ops team's job overnight.

• We wouldn't share bank accounts with strangers.

• We wouldn't share house keys with neighbors.

• We wouldn't share passwords with coworkers.

Why do we share databases with other companies' data?