Using temporary system to provide continuous access during application upgrade

A temporary system is described to provide, during an upgrade of an application implemented using an original system, a continuous access to the application. A copy of a first data-set characterizing a first version of the application is generated on the temporary system when the upgrade becomes available. A selective access to the copy on the temporary system is enabled while preventing access to the first data-set on an original system. The first data-set on the original system is upgraded to form a second data-set characterizing a second version of the application, and a testing of the second data-set is performed. When a result of the testing indicates that the second data-set should be implemented, an access to the second data-set on the original system is enabled while preventing access to the copy on the temporary system. Related methods, apparatus, systems, techniques and articles are also described.