Data Isolation

Ensure secure data separation between tenants

Row-Level Security

Financbase uses row-level security (RLS) to ensure that each tenant can only access their own data. Every database query automatically filters by tenant ID.

-- All queries automatically include tenant filter
SELECT * FROM transactions 
WHERE tenant_id = current_tenant_id()
AND user_id = $1;

Benefits:

Automatic tenant filtering on all queries
Prevents accidental data leakage
No code changes needed - enforced at database level
Works with all ORMs and query builders

API-Level Validation

All API requests validate the tenant context before processing. The tenant ID is extracted from the authentication token or request headers.

// Middleware validates tenant context
app.use((req, res, next) => {
  const tenantId = extractTenantId(req);
  if (!tenantId || !isValidTenant(tenantId)) {
    return res.status(403).json({ error: 'Invalid tenant' });
  }
  req.tenantId = tenantId;
  next();
});

Data Encryption

Sensitive tenant data is encrypted using tenant-specific encryption keys, ensuring that even if data is accessed, it cannot be decrypted without the tenant's key.

Encryption Strategy:

Tenant-specific encryption keys
AES-256 encryption for sensitive fields
Key rotation policies per tenant
Encrypted backups with separate keys

Common Pitfalls to Avoid

These common mistakes can lead to data leakage between tenants:

❌ Forgetting Tenant Context

Always include tenant_id in queries. Never query without tenant filtering.

❌ Sharing Resources Between Tenants

File storage, caches, and other resources must be tenant-scoped.

❌ Exposing Tenant IDs in URLs

Use session-based tenant identification instead of URL parameters when possible.

Best Practices

Follow these practices to ensure proper data isolation:

Always validate tenant context at the API layer
Use database-level RLS policies as a safety net
Test cross-tenant access attempts regularly
Audit logs should include tenant context
Use separate encryption keys per tenant
Implement tenant-specific rate limiting
Regular security audits for isolation vulnerabilities