Max works only with savings accounts, not CDs. However, the yields available through Max are often significantly higher than even a 5 year CD at most brick-and-mortar banks.
The online banks supported on the Max platform do offer CDs that in some cases pay higher rates than their savings accounts. Since with Max you have a direct relationship with each bank, you can easily add CD products at any time by visiting each bank's website. However, Max's optimization process only applies to savings accounts, since CDs involve locking up funds for longer periods of time. Savings accounts offer daily liquidity.