System and methods for providing a Scalable Relational Database Service (SRDBS) are disclosed. SRDBS may allow a subscriber to lease/rent a virtual relational database (a.k.a. namespace) with a specified allocation of disk space, CPU resources and/or I/O resources. The namespace may resemble a physical RDBMS, and may allow client applications to perform SQL queries. SRDBS may partition a subscriber's database across multiple database servers automatically and may replicate each partition automatically. SRDBS may provide automatic routing of client queries to the appropriate database server holding the required data. The routing process may mask temporary data outages due to database replica failures, network failures, and/or repartitioning operations. SRDBS may employ partition maps to convey the location of data to client-side routing functions. These partition maps may use a multi-versioning scheme. SRDBS may provide a resource isolation mechanism that limits the resource utilization of each namespace to its specified allocation.