Quite a bit more than you seem to think.
https://engineering.gusto.com/how-ach-works-a-developer-pers...
Strictly speaking the primary means in which money moves in the United States from a volume perspective is ACH today. That system is a T+1 day from a default perspective, but it has offered the option to same-day settle during a handful of batches throughout a business day. However, ACH is not irrefutable and so it is common to have holds associated with this movement of money.
FedNow is truly 24/7/365 and push only.
All payment flows are subject to an end-to-end payment timeout clock of 20 seconds, starting from the creation timestamp to the point at which the recipient FI (almost always really a Service Provider on their behalf) sends a formal response that they intend to accept or reject the message.
An accepted payment must then be posted to the receiving account "as soon as practicable, but no longer than a few seconds” unless there are compliance/fraud concerns.
In practice, it should rarely take 23 seconds and will likely take 1-5 seconds from an end-to-end perspective depending on the processing speed of the originator, receiver and FedNow Service itself.
And this should be available to customer investors (dudes at home) before retail investors (hedge funds)
The only limitation is that if you day trade, you'll need $25k in your margin account. If you don't day trade or you have $25k, you can withdraw $0.01 a few milliseconds after selling $0.01 in shares
[1]: https://explore.fednow.org/resources/technical-overview-guid...
Light travels about 300km in one millisecond in a vacuum, about 200km in optical fiber. The best achievable theoretical fiber optic RTT for NYC-LA is about 35-40ms. In practice 65ms+ is more realistic due to routing overhead and the fact that cables aren’t always laid in a great circle. This being a financial API with three parties involved in most transactions (the two banks and the fed clearinghouse) there is sure to be more than one round trip involved for TLS establishment, authentication, verification of funds and account availability etc, many of which involve traversing many inevitably complicated systems on each side. It would shock me if such a system could realistically target anything less than 500ms P50.
There are physical bank note, database from different system in trust or untrusted parties that need to be cross checked and reconsolidated
Also I'm not sure if ACID is sufficient or not for banking systems.
DuckDB and SQLite easily handle terabytes of data. They're just not so much for cloud based apps, or things that need multiusers and access control junk. They're the best choice for just about everything else though.
