B2B SaaS (organizations / multi-tenant): Next.js + Postgres + Better Auth

• Customers are companies with several users each, not individuals
• You need invites, roles, and one customer's data kept strictly apart from another's
• Enterprise buyers ask for SSO (SAML or OIDC) and an audit trail
• A small team maintains one codebase for the marketing site and the app

Every table a customer owns carries an organization ID in one shared Postgres database, and every tenant query goes through a single scoped data-access layer — that layer, not scattered filters, is what keeps customers apart. Better Auth's organization plugin supplies organizations, members, invitations, roles, and teams; its SSO plugin adds SAML 2.0 or OIDC sign-in per organization. Next.js runs the membership and role check on the server before any query, and Prisma keeps those queries typed. Writing audit-log rows in the same transaction as the change gives enterprise customers their trail. Postgres Row Level Security is an optional backstop behind the data layer, not a replacement for it.

Each example links to a public source — no claims about private internals.

Skip if your customers are individuals, not organizations — per-tenant scoping, roles, and SSO add weight a single-user app never uses.