For on-demand migration of data in a distributed memory storage configuration, an identifier is transformed at a client into a transformed identifier. From a current configuration of a first plurality of servers operating on a server-side at a current time, a current server is identified at the client. From a previous configuration of a second plurality of servers operating on a server-side at a previous time, a previous server is identified at the client. A first request is sent to the current server to perform an operation using the identifier. A second request is sent to the previous server to perform the operation using the identifier. When a first data in response to the first request is invalid and a second data in response to the second request is valid, the second data is migrated to the current server in a migration request from the client to the current server.