I think there's a lot to be said for just buying short-term treasuries in this environment. What is often missed in a ultra-low interest rate environment (which we are very slowly emerging from) is the risk of catastrophic losses in longer-maturity bond funds in the event of a flight to safety during a market panic. Given the yield curve you are simply not being compensated for taking on term risk.
This article does a good job of parsing CD/Treasury/MM returns:
https://thefinancebuff.com/treasury-bills-cd-money-market.html
Personally I prefer to take my risk on the equity side - which is why 100% of my 60% fixed income allocation is in 1 year T notes and Vanguard Short Term Treasury.
I also recommend Todd Tresidder's article on the bond market bubble from a couple of years ago. The key take-aways still apply in terms of longer-maturity bonds being arguably riskier than stocks in the current environment. This is also talked about at length in Larry Swedroe's newly-revised edition of "Avoiding the Risk of Black Swans" which focuses on the need for alternative investments in a market in which stocks are overvalued and the bond market's flirtation with an inverted yield curve signals danger ahead.
https://financialmentor.com/investment-advice/investment-strategy-alternative/bond-bubble/9064