Networking Study Portal

TL;DR

You do not need to recite the OSI model, but you do need to know which network facts change a design. The ones that matter are: a round trip has a floor set by physics, so cross-region synchronous calls cannot be optimised below roughly 100ms; TCP guarantees ordering and delivery at the cost of head-of-line blocking and connection setup; load balancers operate at either layer 4 or layer 7 and the choice determines what routing decisions are possible; and the "how do I push updates to a client" question has four standard answers with genuinely different trade-offs, of which WebSockets is the most expensive and most often the wrong one.