Medium · 12 steps · ~60 min

Design a multi-tenant SaaS platform

Share one platform between hundreds of customers without letting any of them hurt the others.

A software company serves hundreds of customers (tenants) from one platform. Sharing is what keeps it affordable, but one tenant's traffic spike or data-hungry job must not slow everyone else, and no tenant may ever see another's data.

Same problem as SalesforceShopifySlack

How it works

• Every request is tied to a tenant from the caller's credentials.
• Capacity is shared, but each tenant has a limit and a placement.
• Premium tenants may get stronger isolation for a higher price.

What you'll build

1. A tenant-aware API and data model
2. A gateway and cache for the shared path
3. A rate limiter that stops a noisy neighbour
4. Sharding by tenant and isolation tiers
5. Cheap background compute, and surviving a cold cache and a lost primary

Steps

1. 1Design the API
2. 2Design the data model
3. 3Serve 1,500 requests per second
4. 4Add a gateway and cache at 10,000 requests per second
5. 5Stop a noisy neighbour at 90,000 requests per second
6. 6Global limit or per-tenant limit?
7. 7Shard by tenant at 40,000 requests per second
8. 8Isolation tiers
9. 9Run tenant background jobs cheaply
10. 10Survive a cold cache at 12,000 requests per second
11. 11Lose the primary database
12. 12Deep dive: preventing cross-tenant leaks