The values of various operating and/or configuration parameters of a data environment are managed using a set of self-service Web services and interfaces of a separate control environment. A customer can submit a Web services call into an externally-facing application programming interface (API) or other such externally-facing interface of the control environment. The API receiving the call, as well as information extracted from the call, can be used to determine appropriate adjustments to be performed in the data environment. A workflow can be instantiated that includes tasks used to validate and/or apply the adjustments to the target resources, such as databases, data instances, data stores, instance classes, etc. Various real-time functions such as monitoring and auto-scaling also can be performed via the control plane.