Sync Vs Relationships

Re: For example, if I have 4 apps intertwined with cross app relationships, and then a 5th app has a single cross app relationship with one of those 4 apps, did I just lock that 5th app in with the rest of those?

Exactly.

Even a report link field will cause two apps to become dependent, and run on the same server process.

If you go to the home page and suffix the url with

?a=ListExternalDependencies [Edited after original post]

It will tell you which other apps are under the same server process and why.

At the very core of native QuickBase it can only do one thing at a time. So if you bind five apps together that means they load under the covers as if they were one giant application. So that means if the app takes one second to load a report for one user, it could mean that 99 other users are potentially delayed. So if you have apps with a lot of data and a lot of users all of those clicks are trying to squeeze through just one server process.

If you keep the Apps separate then every app runs independently on its own server process and hence the only competition for that server process is from within that single app.

That is why for example every time you do a cross app relationship there is a pop-up warning you that you may be contaminating two apps to be part of one server process.  So you have to think ahead to how big the two apps are and how much data they will have and how many users they will have to decide whether the convenience of Cross App Relationships and Cross App Report Link fields is worth the potential performance hit.