1. A method comprising: receiving first user request at a cluster of application servers, the first user request to be processed via a first server version; processing, via the first server version, the first user request at a first set of application servers of the cluster of application servers while a second set of application servers of the cluster of application servers is being updated from the first server version to a second server version or a third server version, wherein the first set of application servers is associated with the first server version; dynamically holding one or more user requests in a spin mode while the second set of application servers is being updated to the second server version or the third server version, wherein the one or more user requests include a second user request to be processed via the second server version or a third user request to be processed via the third server version; and selectively routing, from the spin mode, the second user request or the third user request to the second set of application servers for processing upon completion of the update of the second set of application servers to the second server version or the third server version, respectively.