Option 1: Shared database, shared schema (easiest)
  users table: [id, tenant_id, name, email]
  Every query: WHERE tenant_id = ?

Option 2: Shared database, separate schemas
  tenant_1.users, tenant_2.users

Option 3: Separate databases per tenant (most isolated)
  db_tenant_1, db_tenant_2

prisma
model Organization {
  id        String   @id @default(cuid())
  name      String
  plan      Plan     @default(FREE)
  members   Member[]
  projects  Project[]
  createdAt DateTime @default(now())
}

model Member {
  id             String       @id @default(cuid())
  userId         String
  organizationId String
  role           Role         @default(MEMBER)
  user           User         @relation(fields: [userId], references: [id])
  organization   Organization @relation(fields: [organizationId], references: [id])
  
  @@unique([userId, organizationId])
}

typescript
// Create checkout session
const session = await stripe.checkout.sessions.create({
  customer: customerId,
  mode: 'subscription',
  line_items: [{
    price: 'price_pro_monthly',
    quantity: 1,
  }],
  success_url: '{DOMAIN}/billing?success=true',
  cancel_url: '{DOMAIN}/billing?canceled=true',
});

// Webhook handler for subscription events
export async function POST(req: Request) {
  const event = stripe.webhooks.constructEvent(body, sig, secret);
  
  switch (event.type) {
    case 'customer.subscription.created':
      await activatePlan(event.data.object);
      break;
    case 'customer.subscription.deleted':
      await deactivatePlan(event.data.object);
      break;
    case 'invoice.payment_failed':
      await handleFailedPayment(event.data.object);
      break;
  }
}

typescript
const PLAN_FEATURES = {
  FREE: {
    maxProjects: 3,
    maxMembers: 2,
    apiCalls: 1000,
    features: ['basic_analytics'],
  },
  PRO: {
    maxProjects: 50,
    maxMembers: 20,
    apiCalls: 100000,
    features: ['basic_analytics', 'advanced_analytics', 'api_access', 'custom_domain'],
  },
  ENTERPRISE: {
    maxProjects: Infinity,
    maxMembers: Infinity,
    apiCalls: Infinity,
    features: ['basic_analytics', 'advanced_analytics', 'api_access', 'custom_domain', 'sso', 'audit_log', 'sla'],
  },
};