  This paper proposes a novel multi-layer blockchain architecture for the
cross-border trading of CBDCs. The permissioned layer-2, by relying on the
public consensus of the underlying network, assures the security and integrity
of the transactions and ensures interoperability with domestic CBDCs
implementations. Multiple Layer-3s operate various Automated Market Makers
(AMMs) and compete with each other for the lowest costs. To provide insights
into the practical implications of the system, simulations of trading costs are
conducted based on historical FX rates, with Project Mariana as a benchmark.
The study shows that, even with liquidity fragmentation, a multi-layer and
multi-AMM setup is more cost-efficient than a single AMM.
