One was Facebook. I did just find that their prep guides are apparently public on their website, so here was the one I was given for the tech screen, which was heavy on data structures (look for "our comprehensive Facebook Technical Screen Guide" link to the PDF):
https://www.metacareers.com/swe-prep-techscreen/
And heres the one I was given "the loop" interview (theres a link "our comprehensive Facebook Onsite Interview Guide" in the first paragraph):