For me the TL;DR would be: Our edge nodes originally had full BGP tables from our upstreams. This was good as our nodes care about path selection. When we needed to scale, we didn't want to use a pair of (expensive) routers, because we didn't actually need routing, but our upstream were not happy about having to peer to more than a pair of devices. We bought some switches, reflected BGP routes to the nodes, and had to hack L2 connectivity between the switch and the nodes.
For me the TL;DR would be: Our edge nodes originally had full BGP tables from our upstreams. This was good as our nodes care about path selection. When we needed to scale, we didn't want to use a pair of (expensive) routers, because we didn't actually need routing, but our upstream were not happy about having to peer to more than a pair of devices. We bought some switches, reflected BGP routes to the nodes, and had to hack L2 connectivity between the switch and the nodes.
Also, using FIB to describe RIB irks me.