I think a lot of the time when people say the network is slow. They really mean their backend is slow.

With a fast backend ~1-5ms response times (not even that fast). Streaming compression over something like SSE to keep your response sub 1kb packet (roughly an ethernet MTU).

With a push based model, pushing data to a user is half their RTT latency. They will only experience their full RTT on actions they trigger.

Now the network to you is distance to the server (not your rail/nextjs backend taking 400ms). Things like 4G and 3G are fine. The real problem is when you have such bad signal you effectively have no down or up.

More to the point it's that the server has to retrieve and massage data from several docker services to retrieve the full context needed to process the request

A lot of that is ultimately ping time, too though. Like making a naive number of round trips to a database not on the same machine.

How long the server takes to process the 42 requests ahead of you in line, or possibly how long the 318 poorly architected microservices take.