Central Bank Digital Currrency (CBDC) has been proliferated since 2014. Since then, some countries have implemented the one-tiered system or two-tiered system in management.
One-tiered system is that the central bank takes charge of issuance and intermediary (account management, transaction verification) regarding CBDC
Two-tiered system is that the central bank takes charge of issuance CBDC while intermediary (account management, transaction verification) is taken charged by commercial banks and other financial institutions.
From what I read so far, Cambodia is the country has already implemented one-tiered system for CBDC management (here)
China is the country which already followed two-tiered system (here)
I am looking for what countries already implemented their CBDC and which system (one-tiered or two-tiered) they follow (with references)