I Built a 12-Module Multi-Tenant SaaS Platform Alone. Here's the Architecture That Made It Possible.

Originally published on rohitraj.tech

The SaaS market hits $465B in 2026 and 70% of vendors use multi-tenancy. I built RetailOS — a 12-module Spring Boot monorepo with billing, inventory, GST invoicing, khata ledger, and offline sync — as a solo engineer. Here's every architecture decision.

---

Read the full version with code samples, diagrams, and architecture details: I Built a 12-Module Multi-Tenant SaaS Platform Alone. Here's the Architecture That Made It Possible.

More engineering notes: rohitraj.tech/notes