Multi-Tenant Architecture

Multi-Tenant Architecture

Designs multi-tenant systems with data isolation, tenant-aware routing, and resource quotas.

Decision Framework

When to Apply

Use when: SaaS applications, white-label solutions, enterprise with divisions, B2B platforms

When NOT to Apply

Don't use when: Single-tenant app, personal projects, consumer apps

Anti-Patterns

1. No Tenant Isolation

// BAD: Any user can access any tenant's data
const orders = await db.query('SELECT * FROM orders WHERE id = ?', [orderId]);

// GOOD: Always scope by tenant
const orders = await db.query('SELECT * FROM orders WHERE id = ? AND tenant_id = ?', [orderId, tenantId]);

2. Shared Sessions Across Tenants

Always scope sessions and caches by tenant ID.

Trigger Phrases

• "Multi-tenant"
• "Tenant isolation"
• "SaaS architecture"
• "White-label"
• "Data segregation"

Patterns

Tenant Resolution Middleware

const tenantMiddleware = async (req, res, next) => {
  const tenantId = req.headers['x-tenant-id'] || extractSubdomain(req.hostname);
  if (!tenantId) return res.status(400).json({ error: 'Tenant not specified' });
  
  const tenant = await tenantService.get(tenantId);
  if (!tenant || tenant.status !== 'active') return res.status(404).json({ error: 'Tenant not found' });
  
  req.tenant = tenant;
  req.db = getTenantConnection(tenant.id);
  next();
};

Isolation Models

Integration

• Works with: database-schema-designer, authentication-flow-designer, feature-flag-system