Quick answer
Multi-tenant means many customers share one app and one database. Each customer's data is kept separate.
What it is
Multi-tenant means one app serves many customers. Each customer's data is isolated in the same database. One update reaches all customers.
Why it matters
Multi-tenant is what makes SaaS cost-effective. A separate stack for each customer would cost more and slow down every release.
How to use it
- Add a tenant_id to every database row from day one.
- Use row-level security to keep each customer's data apart.
- Watch for accidental cross-tenant data leaks.
- Set rate limits to prevent noisy neighbour issues.
Examples
- Salesforce, Slack and Notion are multi-tenant SaaS.