Comment by antonvs
A lot of settlement in financial markets is still pretty slow. That’s a big reason why there was so much fintech interest in blockchain.
You may be thinking of high frequency trading. In that case, traders interact directly with an exchange - e.g. via direct market access[1] - so it’s a pre-established two-party interaction. There’s no particular technical difficulty with making that fast. Usually, slow transaction times are a consequence of the structure of the market, not a technical issue particularly.
[1] https://corporatefinanceinstitute.com/resources/career-map/s...
In the broad picture of engineering, I would consider this to be technically difficult. Many pieces of the puzzle need to interact correctly to remove latency, from physical location, network gear, decision about where software runs, removing unnecessary layers of everything, to algos and data structures, and doing razor-tight tradeoff analysis favoring low-latency at every step along the way. It’s also expensive. So it’s hard to agree that this is not hard. On the flip side, if you find this easy and want a job, msg me.