[tomalpha]

FPGA clocks run at about 1/10th of the speed of a general purpose CPU (very very roughly).

They can do more work per clock-cycle either using dedicated processing logic for a particular operation (some bit twiddling stuff like crypto can take advantage of this), pipelining multiple requests in serial, or processing multiple different requests at exactly the same time in parallel.

Crucially, whichever method(s) you use, you need to achieve more than 10 times the work-per-clock to make up for the clock being 10 times slower.

FPGAs are harder to program, have fewer and less well-rounded toolchains and are much much much harder to debug than other software. A bug tends to simply freeze the system completely for example.

An HTTP server on an FPGA where the FPGA isn't just emulating a general purpose CPU (a so-called "soft core") at a slow clock speed? Yes it's do-able: https://news.ycombinator.com/item?id=11776190, but it's questionable whether it would ever be faster than something written on an x86 CPU.