You don't specify if data on front ends is read-only or the type of link between frontend and backend.

Anyway I've always been a big fan of FederatedX which might still work:

You can create a connection on the front-end systems and then create a projection of each needed table in one of two ways:

1) create a federated table in the front end pointing to a back-end table and then a local view for the column restriction

2) create a view on the backend and a federatedx table at front end pointing to the view on the backend