Strip away the brand names and every interbank switch does the same four things. It routes a payment instruction from one institution to another. It netsthe day's flows so banks move one balance instead of millions of gross transfers. It clears — confirms the obligation is good — and finally it settles, moving central-bank or reserve money to extinguish the debt.
Card networks, automated clearing houses, real-time gross settlement systems, and the correspondent-banking mesh behind cross-border payments are all variations on this. And all of them share one structural fact: the switch is an operated intermediary. Someone runs it. That someone sets the batch windows, holds the settlement risk in between, decides who connects, and — at the cross-border end — interposes a chain of correspondents each taking a cut, a day, and a measure of discretion.
That is why a domestic transfer can clear in seconds while a cross-border one still takes days: not because the math is hard, but because the switch is a stack of trusted operators reconciling with each other. The intermediary is the latency, the cost, and the risk.