in fact, there IS a solution for this which has been live for a long time: FiRM by @InverseFinance instead of a @NotionalFinance style zero-coupon bond, FiRM provides fixed-rate borrowing by tokenizing borrow rate into DBR (dola borrow rate). 1 DBR gives you the right to borrow 1 DOLA (@InverseFinance's own stablecoin) for 1 year. say you want to borrow 1,000 DOLA for 1 year, which requires 1000 DBR in your wallet, and you buy DBR at a price of $0.04, then the fixed borrow rate you are paying is effectively 4% annualized. and it's super flexible as well: if you want to exit earlier, you can just repay the loan, and sell the unused DBR. you can also borrow more DOLA without purchasing more DBR, as long as you are fine with reduced duration. for example, the same 1000 DBR can be used to support 2000 DOLA loan which will expire in 6 months. this model does have problems: 1) lenders (DOLA liquidity providers) don't get fixed rate. 2) relies on its own CDP stablecoin, difficult to apply to other stablecoin lending markets. still, i think this is the most elegant solution DeFi can have for fixed-rate lending. even its "problems" are just demonstrations of two facts: 1. it's impossible to get fixed rates + instant liquidity without a secondary market of yield (DBR is itself this yield market) 2. overcollateralized stablecoins CAN outcompete USDC in many areas because as a user, you can issue the former, but not the latter