The multi-tenant SaaS checklist: seven decisions, what each costs if you defer it, and the one everyone worries about far too early. Overview # Decision Decide by Cost if deferred 1 What is a tenant? Day one Rewrite every query 2 How does a request resolve to a tenant? Day one The most common real breach 3 Where does isolation live? First paying customer Audit everything you wrote 4 Roles, or permissions? Customer thr...