You are not talking about an insane amount of data if it's 56 Gbit/s. Of course a caching server could handle that.
Source: Has written servers that saturated 40gig (with TLS) on an old quadcore.
If you need to go to disk to serve large parts of it, it's a different beast. But then again, Netflix was doing 800gig already three years ago (in large part from disk) and they are handicapping themselves by choosing an OS where they need to do significant amounts of the scaling work themselves.
What I've been referring to is the fact that even unlimited 1 Gbps connections can be quite expensive, now try to find a 2x40 gig connection for a reasonable money. That one user generated 200 TB in 24 hours! I have no idea about bandwidth pricing, but I bet it ain't cheap to serve that.
Presumably a caching server would be 10GbE, 40GbE, or 100GbE
56Gbit/sec of pre-generated data is definitely something that you can handle from 1 or 2 decent servers, assuming each request doesn't generate a huge number of random disk reads or something