Valkey 9.0 introduces the concept of numbered databases, which significantly enhances the architecture of distributed caching systems by allowing logical separation of keys without the need for key prefixing. This feature, reminiscent of Redis's early design, permits data within the same key name to exist separately across different databases, thus enabling efficient multi-tenancy, instant data switching for use cases like e-commerce pricing changes, and parallel test environments without data collision. Valkey's approach eliminates the overhead of data migration and network transfer, offering a seamless way to move data between databases through simple pointer changes. This development simplifies multi-tenant applications, enhances the safety of A/B testing and CI environments, and reduces the risks associated with rollouts and migrations. Future enhancements may include named databases, per-database memory limits, and rate limiting, which will further bolster resource isolation and developer experience.