Currently i'm working on a small platform with a simple client-server model and will soon go in a closed beta with a launching customer.
In essence it's an Electron application which is mostly used for logging in, and fetching files/information from a simple PHP+MySQL backend with some other related functionality regarding those files.
One of the requirements is that it needs to be able to update. Now i have been able to update the application itself trough Amazon S3, which actually works quite nicely. But here is where i run into some problems.
Some clients in the future, might object to the backend that we provide, and want a 'copy' of our backend to use for their own users (hosting accounts, files that they use etc. even though we are the ones providing those files and end-users not having any direct access to it.).
This objection will come from a security and control standpoint. I however, will have no access (obviously) to these servers directly.
What is an acceptable manner of releasing updates for these backends? ( which will be PHP files and changes in the form of queries to the database). Also, i might not want to release a new 'client' version while some users still use a deprecated on-premise backend.
ANY helpful information is very welcome, since i'm a jr. softw. engineer and 'one-man-army' in a small company. Please ask questions if it helps in giving answers.