Abstract: Techniques for enabling efficient data migration between data stores with no downtime are disclosed. A distributed computing system can be implemented with an initial data store and a target data store. During the migration of a portion of the data from the initial data store to the target data store, the distributed computing system can receive requests to create data entities or launch workflow instances at the data stores. The system can determine whether the initial data store or the target data store has been designated the primary data store for handling the requests. The system can also determine whether the initial data store or the target data store contain a key associated with the request. If the key is present in either of the data stores, the system may abort the creation of the data entity.