I had the impression that they are still run like mostly independent companies who only share some data on the backend.

AFAIK, I remember reading something about Instagram moving into Facebook datacentres some time ago. I believe they were on AWS before the acquisition.

Yeah that's what I was thinking too, so this is probably DNS related.

Might I ask what’s SPOF?

Single Point of Failure.

Thanks

Single Point Of Failure

Ta