Can you build multi-tenant SaaS applications?

Absolutely! Multi-tenant SaaS serves multiple customers from single application instance. Architecture patterns include: shared database with tenant ID (cost-effective, simpler), separate databases per tenant (data isolation, more complex), or hybrid approaches (shared infrastructure, isolated data). Multi-tenant features: tenant provisioning (automated signup creates new tenant), data isolation (tenants never see each other's data), customisation per tenant (branding, settings, features), usage tracking (monitor per-tenant consumption), billing integration (Stripe subscription per tenant), and admin panels (manage all tenants). Popular SaaS applications: project management tools (Asana, Trello), accounting software (Xero, QuickBooks Online), CRM platforms (Salesforce, HubSpot), and helpdesk systems (Zendesk, Freshdesk). Benefits of multi-tenant: efficient resource usage, centralised updates (all tenants updated simultaneously), easier maintenance, and lower infrastructure costs. Challenges include: security (preventing data leaks between tenants), customisation (balancing flexibility with maintainability), and performance (ensuring one tenant doesn't impact others). Multi-tenant architecture enables SaaS business models with recurring revenue.