Follow up on my previous post: How do large ISPs (i.e. AT&T, Verizon, Level 3, BT, Orange) tend to handle route injection, BGP aggregation, and RR placement?

I posted this (https://www.reddit.com/r/networking/comments/hkwu1t/service_providers_where_do_you_choose_to/) yesterday and I got a lot of great responses. However, they seemed to be from the perspective of smaller or mid-sized service providers, when I'm more interested in hearing about how the big guys do it. I imagine they'd have to do some amount of aggregation internally, since if they injected every /29 or /30 into iBGP, on top of the entire internet routing table, it'd get out of control.