5ms reaction time mentioned on these slides are far cry for what computers can do. trading servers reaction time packet-in packet-out even without fpga can take as little as 20 microseconds.
- cpu thermal profiles and power governors
- cpu affinity
- non-evented io(if you prefer latency over the number of clients served)
- network interrupt coalescing(actually, disabling coalescing), network msi-x, hardware offloads, 10gb fiber or DAC connections(very cheap nowadays)
- lock-free and kinda-crdt data structures(between threads)
- predictable memory allocations(better - no allocations on critical path)
- specialized logging and tracing(no stdio)
can drive you quite far.
There is a big crossover in tech with shortwave band military over the horizon communications systems, and also serious ham radio enthusiasts who use big yagis and antenna rotators to talk to each other from opposite sides of the planet.
Things like chained 6 and 11 GHz microwave between NY-Chicago, which was the "hot new thing" in HFT 7-8 years ago to achieve better than fiber latency on that route, seem quaint now.