Reserve Bank uses the SAMOS system to clear interbank transactions. It's their own system and the only settlement system in the country. Clearing is done by either Visa, Mastercard or Bankserv for normal banking and Strate for equities. Clearing house will depend on the bank. As mentioned the delay is due to most transactions being batch settled between banks and SARB.
SAMOS is one of the best system in the world and we built it ourselves.
Yes lots of kak in SA banking, but we have one of the what banking systems in the world.
Our baking apps however are k@k and that's partly due to the majority of SA not being tech savvy vs the US and people still use ussd for banking etc. So there's no push from banks to upgrade their interfaces.
And on boarding clients is also limited by government thanks to no e-rica and e-fica they should've just adopted a proper digital KYC/AML process.