Caches are to trade off latency and bandwidth for cost. It's cheaper to put normal servers in regional colos to serve a lot of local customers, probably not cheaper to put expensive servers in orbit to serve a varying and small set of customers below a satellite.
I can see running HSMs in space; probably the most cost-effective physical security available.
HSM in space is a compelling idea. You don't need a big satellite either. You really just need to keep a few hundred bytes of key material and then process crypto operations against it from the ground.
I can see running HSMs in space; probably the most cost-effective physical security available.