Designing Scalable Multi-Tenant SaaS Backends Supporting 300K+ Users

When scaling a B2B SaaS platform, multi-tenancy enables a single application instance to serve multiple corporate customers while ensuring strict data separation and custom domain routing.

At Arobit Business Solutions, we built a multi-tenant backend architecture serving over 300K+ registered users and processing 50L+ INR monthly.

Tenant Resolution & Routing

We solved custom domain mapping through dynamic NGINX proxy headers passed into our Node.js and Laravel middleware:

Request: customer1.platform.com OR customdomain.com
                    │
                    ▼
          NGINX (Reverse Proxy)
     Sets Host & X-Tenant-Domain
                    │
                    ▼
          Tenant Resolution Middleware
   (Lookup Tenant by Hostname in Redis Cache)
                    │
                    ▼
     Scoped Database Schema / Row Context

Payment Processing Integration

Handling global and domestic billing across tenants required integrating both Stripe and Razorpay with automated webhook verification, recurring subscription state machines, and idempotent charge processing.