Saas Platforms

This covers the practical architecture of SaaS applications: multi-tenancy strategies (shared database with tenant_id, schema per tenant, or database per tenant), Stripe subscription management with prorations and webhooks, and usage-based billing. The tenant isolation patterns are especially useful, including Prisma middleware for automatic filtering and PostgreSQL row-level security examples. It's aimed at the point where you're building something more sophisticated than a simple app but not yet at hyperscale. The feature flags and entitlement checking code helps you gate features by plan tier. If you're implementing billing or trying to prevent data leaks between tenants, this gives you the patterns that actually matter in production.