Comment by namibj

> There's a reason buildings with high bandwidth constraints huddle near internet backbones.

Yeah because interaction latency matters and legacy/already buried fiber is expensive to rent so you might as well put the facility in range of (not-yet-expensive) 20km optics.

> Copper doesn't work over these kinds of distances without powered switches, which adds latency.

You need a retimer, which adds on the order of 5~20 bits of latency.

> And that becomes a huge problem if you want to do any real-time work like DB replicas.

Almost no application would actually require "zero lost data", so you could get away with streaming a WAL or other form of reliably-replayable transaction log and cap it to an acceptable number of milliseconds of data loss window before applying blocking back pressure. Usually it'd be easy to tolerate enough for the around 3 RTTs you'd really want to keep to cover all usual packet loss without triggering back pressure.

Sure, such a setup isn't cheap, but it's (for a long while now) cheaper than manually fixing the data from the day your primary burned down.