Embodiments of the present invention are directed to a two-way data transfer and synchronization system. The data transfer and synchronization system includes a provider system and a customer system. The provider system includes a web service hosted by a web server connected to a computer network and a first database. The customer system includes a client application, connected to the computer network and a second database (e.g., SIS database). The provider system cannot read data from the second database. The client application is configured to send requests to the web service and to receive HTTP responses from the web service. The responses from the web service are executed by the client application so that changes made to the second database are also made to the first database, and vice versa.