In 2025, multi-tenancy becomes essential for building any SaaS or product, and while often perceived as complex, it can significantly reduce infrastructure costs when implemented correctly. There are three main approaches to multi-tenant architecture: Row-Level Tenancy, which is simple but may impact performance at scale; Schema-Level Separation, which balances cost and isolation by allocating each tenant a distinct schema; and Database-Level Isolation, which offers high security at a higher expense by providing each tenant with an individual database. Performance can improve by 20-30% with an appropriate setup, and tools like Flyway or Liquibase for migrations, PostgreSQL for database management, and PgBouncer for connection pooling are recommended. Mistakes to avoid include aiming for a perfect solution from the start, neglecting backup and restore processes, and sharing connection pools between tenants. Starting with Row-Level Tenancy is often sufficient for most applications, and a simple, effective architecture can ensure data security and manageable costs.