Firestore Architecture For Scaling Read-Intensive Multi-Tenant Software

When you research how to build a multi-tenant SaaS on Firestore, most articles stop at one idea: put a tenantId field on every document . That's true, but it's the easy half. The more tricky question is how do you arrange your collections so that reads, writes, and costs stay within budget as the business scales. Background I was afraid of creating a system that was more trouble and expensive than it was worth. I built a multi-tenant SaaS Trogern for managing informal taxi businesses in Zimbabwe