Updating a distributed backend and keep track of compatible releases for Electron app + Webserver (PHP + MySQL )

Question

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.

Answer 1

Introduce versioning

Not a nice situation. I guess the answer is explicit versioning.

You will need to be explicit about which version of the backend your frontend requires. And the frontend must either support at least two versions of the backend ("current" and "previous") or you must operate and support two versions of the frontend (one for current backend, one for previous). Many small changes to the frontend are not a problem, but changes requiring a different backend are.

The backend operators need to accept that once their version has fallen back to be "previous" they need to update soon, before it becomes "previousprevious" and the application breaks.

Something like this. Sounds like difficult negotiations to me.