A system, comprising: one or more processors; a memory coupled to the one or more processors; and one or more storage nodes; wherein the memory stores program instructions that when executed by the one or more processors cause the one or more processors to implement a database service that provides database services in both a multi-tenant environment and a single-tenant environment to one or more database service clients, wherein a multi-tenant environment comprises an environment in which database tables for multiple clients are hosted collectively in a single database instance, and wherein a single-tenant environment comprises an environment in which database tables for different clients are hosted in different database instances; wherein the database service is configured to: receive a request from a client to create a database instance, wherein the request specifies that the database instance is to be created in a multi-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a multi-tenant environment on behalf of the requesting client; receive a request from a client to create another database instance, wherein the request specifies that the another database instance is to be created in a single-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a single-tenant environment on behalf of the requesting client, wherein the created database instance in the multi-tenant environment and the created another database instance in the single-tenant environment are both maintained by the database service; receive a request from a client to create a table, wherein the request specifies whether the table is to be created in the database instance in the multi-tenant environment or in the another database instance in the single-tenant environment; and create a table in a database instance in the specified environment. one or more processors; a memory coupled to the one or more processors; and one or more storage nodes; wherein the memory stores program instructions that when executed by the one or more processors cause the one or more processors to implement a database service that provides database services in both a multi-tenant environment and a single-tenant environment to one or more database service clients, wherein a multi-tenant environment comprises an environment in which database tables for multiple clients are hosted collectively in a single database instance, and wherein a single-tenant environment comprises an environment in which database tables for different clients are hosted in different database instances; wherein the database service is configured to: receive a request from a client to create a database instance, wherein the request specifies that the database instance is to be created in a multi-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a multi-tenant environment on behalf of the requesting client; receive a request from a client to create another database instance, wherein the request specifies that the another database instance is to be created in a single-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a single-tenant environment on behalf of the requesting client, wherein the created database instance in the multi-tenant environment and the created another database instance in the single-tenant environment are both maintained by the database service; receive a request from a client to create a table, wherein the request specifies whether the table is to be created in the database instance in the multi-tenant environment or in the another database instance in the single-tenant environment; and create a table in a database instance in the specified environment. receive a request from a client to create a database instance, wherein the request specifies that the database instance is to be created in a multi-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a multi-tenant environment on behalf of the requesting client; receive a request from a client to create another database instance, wherein the request specifies that the another database instance is to be created in a single-tenant environment; provision one or more of the one or more storage nodes to create a database instance in a single-tenant environment on behalf of the requesting client, wherein the created database instance in the multi-tenant environment and the created another database instance in the single-tenant environment are both maintained by the database service; receive a request from a client to create a table, wherein the request specifies whether the table is to be created in the database instance in the multi-tenant environment or in the another database instance in the single-tenant environment; and create a table in a database instance in the specified environment.