I wondered what kind of liquidity buffer participating institutions will have to provide in order to insure that instant payments really are instant, even in high demand situations, and found the following, which I don't find very satisfying:<p>> FedNow participants or their correspondents will be expected to maintain balances in their master accounts to settle FedNow transactions, consistent with the Federal Reserve’s Policy on Payment System Risk<p>That's from page 43 of the Customer Readiness Guide [1], linked from the FedNow service home page [2].<p>1. <a href="https://explore.fednow.org/resources?id=10&resourceRole=fi_sp-eu_spe&resourceTitle=readiness-guide" rel="nofollow">https://explore.fednow.org/resources?id=10&resourceRole=fi_s...</a><p>2. <a href="https://www.frbservices.org/financial-services/fednow" rel="nofollow">https://www.frbservices.org/financial-services/fednow</a>