saas

## What I do - Design SaaS architectures and multi-tenancy - Implement tenant isolation strategies - Build metering and billing systems - Configure identity and access for SaaS - Optimize for multi-tenant costs - Implement tenant onboarding flows ## When to use me - When building SaaS products - When implementing multi-tenancy - When designing billing systems - When managing tenant data isolation - When building SaaS infrastructure - When planning SaaS scaling ## Key Concepts ### SaaS Architecture Models | Model | Isolation | Complexity | Cost | |-------|-----------|------------|------| | **Shared Everything** | Database | Low | Low | | **Shared Database** | Schema | Medium | Medium | | **Shared Application** | Container | Medium | Medium | | **Isolated** | VPC/Account | High | High | ### Multi-Tenant Database Schema ```sql -- PostgreSQL multi-tenant schema CREATE TABLE tenants ( id UUID PRIMARY KEY DEFAULT gen_random_uuid(), name VARCHAR(255) NOT NULL, subdomain VARCHAR(63) UNIQUE NOT NULL, plan VARCHAR(50) DEFAULT 'free', created_at TIMESTAMP DEFAULT NOW() ); CREATE TABLE users ( id UUID PRIMARY KEY DEFAULT gen_random_uuid(), tenant_id UUID REFERENCES tenants(id) ON DELETE CASCADE, email VARCHAR(255) NOT NULL, name VARCHAR(255), role VARCHAR(50) DEFAULT 'member', created_at TIMESTAMP DEFAULT NOW(), UNIQUE(tenant_id, email) ); -- Row-level security ALTER TABLE users ENABLE ROW LEVEL SECURITY; CREATE POLICY "tenant_isolation" ON users FOR ALL USING (tenant_id = current_setting('app.tenant_id')::UUID); ``` ### Tenant Context ```python # FastAPI multi-tenancy from contextvars import ContextVar from fastapi import Request, Depends tenant_context: ContextVar[str] = ContextVar('tenant_id', default=None) def get_tenant_id(request: Request) -> str: # Extract from subdomain host = request.headers.get('host', '') subdomain = host.split('.')[0] # Or from JWT # token = request.headers.get('authorization') # tenant_id = decode_jwt(token)['tenant_id'] return tenant_context.set(subdomain) def get_current_tenant() -> Tenant: tenant_id = tenant_context.get() return Tenant.objects.get(subdomain=tenant_id) @app.get("/api/users") async def list_users(tenant: Tenant = Depends(get_current_tenant)): return User.objects.filter(tenant=tenant).all() ``` ### SaaS Identity ```typescript // OAuth2 for SaaS const oauth2Client = new OAuth2Client( process.env.GOOGLE_CLIENT_ID, process.env.GOOGLE_CLIENT_SECRET, 'https://yourapp.com/callback' ); // Multi-tenant SSO const samlConfig = { entryPoint: 'https://idp.example.com/sso', issuer: 'yourapp', callbackHandler: async (profile) => { const tenant = await findOrCreateTenant(profile.orgId); const user = await findOrCreateUser(profile, tenant); return { user, tenant }; } }; // Role-based access for SaaS const permissions = { admin: ['*'], manager: ['read', 'write', 'users:read'], member: ['read', 'write:own'], viewer: ['read'] }; ``` ### Usage Tracking ```python class UsageTracker: def track_event(self, tenant_id: str, event_type: str, metadata: dict): # Record usage event event = UsageEvent( tenant_id=tenant_id, event_type=event_type, metadata=metadata, timestamp=datetime.utcnow() ) self.db.save(event) # Update meter meter = self.get_or_create_meter(tenant_id, event_type) meter.increment(metadata.get('quantity', 1)) def get_usage(self, tenant_id: str, period: Period) -> UsageReport: events = self.db.query(UsageEvent) .filter( tenant_id=tenant_id, timestamp__gte=period.start, timestamp__lte=period.end ) return self.aggregate_events(events) ``` ### Billing Integration ```python # Stripe SaaS billing import stripe stripe.api_key = os.environ['STRIPE_SECRET_KEY'] def create_customer(tenant: Tenant): customer = stripe.Customer.create( email=tenant.admin_email, metadata={'tenant_id': str(tenant.id)} ) tenant.stripe_customer_id = customer.id tenant.save() def create_subscription(tenant: Tenant, plan_id: str): subscription = stripe.Subscription.create( customer=tenant.stripe_customer_id, items=[{'price': plan_id}], metadata={'tenant_id': str(tenant.id)}, trial_period_days=14 ) def get_invoices(tenant: Tenant): return stripe.Invoice.list( customer=tenant.stripe_customer_id, limit=12 ) ``` ### SaaS Best Practices - **Tenant Isolation**: Secure data separation - **Metered Billing**: Track usage accurately - **Scalable Architecture**: Support growth - **Self-Service Onboarding**: Reduce friction - **Feature Flags**: Gradual rollouts per tenant - **Usage Analytics**: Understand usage patterns - **SLA Management**: Define and monitor SLAs