Multi-tenancy is one of those features that sounds simple and isn't. Organizations, team members, role-based access, shared resources -- done wrong, it's a security nightmare. Here's the pattern that works.
The Data Model
Everything starts with the right schema. The core structure: Users belong to Organizations through Memberships.
model Organization {
id String @id @default(cuid())
name String
slug String @unique // URL-safe identifier
plan String @default("free")
createdAt DateTime @default(now())
updatedAt DateTime @updatedAt
members Membership[]
invites OrgInvite[]
// Your product resources:
projects Project[]
apiKeys ApiKey[]
}
model Membership {
id String @id @default(cuid())
userId String
organizationId String
role OrganizationRole @default(MEMBER)
createdAt DateTime @default(now())
user User @relation(fields: [userId], references: [id], onDelete: Cascade)
organization Organization @relation(fields: [organizationId], references: [id], onDelete: Cascade)
@@unique([userId, organizationId])
}
enum OrganizationRole {
OWNER
ADMIN
MEMBER
VIEWER
}
model OrgInvite {
id String @id @default(cuid())
organizationId String
email String
role OrganizationRole @default(MEMBER)
token String @unique @default(cuid())
expiresAt DateTime
createdAt DateTime @default(now())
organization Organization @relation(fields: [organizationId], references: [id], onDelete: Cascade)
@@unique([organizationId, email])
}
The Permission System
Define what each role can do:
// src/lib/permissions.ts
type Permission =
| "org:read"
| "org:update"
| "org:delete"
| "member:invite"
| "member:remove"
| "member:update_role"
| "project:create"
| "project:read"
| "project:update"
| "project:delete"
| "billing:manage"
const ROLE_PERMISSIONS: Record<OrganizationRole, Permission[]> = {
OWNER: [
"org:read", "org:update", "org:delete",
"member:invite", "member:remove", "member:update_role",
"project:create", "project:read", "project:update", "project:delete",
"billing:manage",
],
ADMIN: [
"org:read", "org:update",
"member:invite", "member:remove",
"project:create", "project:read", "project:update", "project:delete",
],
MEMBER: [
"org:read",
"project:create", "project:read", "project:update",
],
VIEWER: [
"org:read",
"project:read",
],
}
export function hasPermission(role: OrganizationRole, permission: Permission): boolean {
return ROLE_PERMISSIONS[role].includes(permission)
}
The Auth Helper
A helper that loads the current user's org membership for every request:
// src/lib/org-auth.ts
import { auth } from "@/lib/auth"
import { db } from "@/lib/db"
import { hasPermission } from "@/lib/permissions"
export async function getOrgMembership(orgSlug: string) {
const session = await auth()
if (!session?.user?.id) return null
const membership = await db.membership.findFirst({
where: {
userId: session.user.id,
organization: { slug: orgSlug },
},
include: { organization: true },
})
return membership
}
export async function requireOrgPermission(
orgSlug: string,
permission: Permission
) {
const membership = await getOrgMembership(orgSlug)
if (!membership) {
throw new Error("Not a member of this organization")
}
if (!hasPermission(membership.role, permission)) {
throw new Error(`Insufficient permissions: requires ${permission}`)
}
return membership
}
URL Structure
Two common approaches:
Subdomain routing (acme.your-app.com): Premium feel, complex to implement, requires DNS config per org.
Path routing (your-app.com/acme/...): Simpler, no DNS complexity, works with Vercel out of the box.
For most indie SaaS products, path routing is the right call:
/[orgSlug]/dashboard
/[orgSlug]/settings
/[orgSlug]/settings/members
/[orgSlug]/projects/[projectId]
// src/app/[orgSlug]/layout.tsx
import { notFound } from "next/navigation"
import { getOrgMembership } from "@/lib/org-auth"
export default async function OrgLayout({
children,
params,
}: {
children: React.ReactNode
params: { orgSlug: string }
}) {
const membership = await getOrgMembership(params.orgSlug)
if (!membership) notFound()
return (
<div>
<OrgSidebar org={membership.organization} role={membership.role} />
<main>{children}</main>
</div>
)
}
Protecting API Routes
// src/app/api/[orgSlug]/projects/route.ts
import { requireOrgPermission } from "@/lib/org-auth"
export async function POST(
req: NextRequest,
{ params }: { params: { orgSlug: string } }
) {
let membership: Awaited<ReturnType<typeof requireOrgPermission>>
try {
membership = await requireOrgPermission(params.orgSlug, "project:create")
} catch (err) {
return NextResponse.json({ error: "Forbidden" }, { status: 403 })
}
const body = await req.json()
const project = await db.project.create({
data: {
...body,
organizationId: membership.organizationId,
createdById: membership.userId,
}
})
return NextResponse.json(project)
}
Resource Isolation
This is the critical security property: users must never see resources from other organizations.
Always filter by organizationId in every query:
// CORRECT: scoped to org
const projects = await db.project.findMany({
where: {
organizationId: membership.organizationId, // ALWAYS include this
}
})
// DANGEROUS: returns all projects, no org scoping
const projects = await db.project.findMany()
A useful pattern: create a scoped DB client that enforces org isolation:
export function createOrgDb(organizationId: string) {
return {
project: {
findMany: (args?: Omit<Parameters<typeof db.project.findMany>[0], "where"> & { where?: Omit<Prisma.ProjectWhereInput, "organizationId"> }) =>
db.project.findMany({
...args,
where: { ...args?.where, organizationId },
}),
// ... other methods
}
}
}
// Usage in route handler -- organizationId is always enforced
const orgDb = createOrgDb(membership.organizationId)
const projects = await orgDb.project.findMany({ where: { published: true } })
Invite Flow
// Create invite
export async function POST(req: NextRequest, { params }) {
const membership = await requireOrgPermission(params.orgSlug, "member:invite")
const { email, role } = await req.json()
const invite = await db.orgInvite.create({
data: {
organizationId: membership.organizationId,
email,
role,
expiresAt: new Date(Date.now() + 7 * 24 * 60 * 60 * 1000), // 7 days
}
})
await sendEmail({
to: email,
subject: `You're invited to ${membership.organization.name}`,
body: `Accept your invitation: ${process.env.NEXTAUTH_URL}/invite/${invite.token}`,
})
return NextResponse.json({ success: true })
}
// Accept invite
export async function POST(req: NextRequest, { params }) {
const session = await auth()
if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
const invite = await db.orgInvite.findUnique({
where: { token: params.token },
include: { organization: true },
})
if (!invite || invite.expiresAt < new Date()) {
return NextResponse.json({ error: "Invalid or expired invite" }, { status: 400 })
}
await db.membership.create({
data: {
userId: session.user.id,
organizationId: invite.organizationId,
role: invite.role,
}
})
await db.orgInvite.delete({ where: { id: invite.id } })
return NextResponse.json({ organizationSlug: invite.organization.slug })
}
This multi-tenant structure -- with org routing, role-based permissions, invite flow, and resource isolation -- is available as a pattern in the AI SaaS Starter Kit.
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