[mrkeen]

I could have labelled the boxes, even though A and C are interchangeable in what I wrote.

A is your React app, C is your Java service, and B is the hypothetical bff that might be inserted between.

Decoupling is not disconnection.

If B is (well-)implemented, your React app and Java service do not know about each other.

[steve1977]

But B needs to know both the React app and the Java service. You’ve just moved the coupling from one component to another.

[mrkeen]

Yes. That's what (de)coupling is.

[boxed]

No, that's not it at all.