# Multi-Tenant Architecture

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

- Skill: `fadil369/multi-tenant-architecture` (Agent Skill)
- Install (CLI): `npx skillmds@latest add fadil369/multi-tenant-architecture`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fadil369/multi-tenant-architecture/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: fadil369 (https://skillmd.com/u/fadil369)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/fadil369/multi-tenant-architecture

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# 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
```javascript
// 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
```javascript
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
| Model | Isolation | Cost | Complexity |
|---|---|---|---|
| Shared DB + tenant_id | Low | Low | Low |
| Schema per tenant | Medium | Medium | Medium |
| Database per tenant | High | High | High |

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