Fauna Serverless Scheduling: Cooperative Scheduling with QoS is a database system designed to support efficient and fair resource sharing in multi-tenant environments. The system avoids traditional pitfalls of static isolation boundaries and auto-scaling groups by implementing cooperative scheduling and Quality of Service (QoS) within its core architecture, making it well-suited for serverless use cases. This approach allows the database provider to benefit from economies of scale while reducing risk and cost for both the serverless user and the provider. Fauna's system provides a fair resource distribution among workloads, efficient context switching, predictable outcomes of batch operations, security through isolation and access control, and fine-grained identity management and access control. By using cooperative threading with async coroutine execution, Fauna can simultaneously run thousands of concurrent queries in a mixed workload setting, making it an attractive solution for teams implementing multi-tenant data architectures.