For a cash bucket, as I have said before, I prefer short-maturity TIPS. They can be sold and get one-day settlement. Spreads are tight and commissions are very low. For example, on the 1.375s of 1/15/20 at $100.665, you get .88% YTM in cash (due to selling above face, you get the full coupon but the bond depreciates) plus CPI inflation, which now looks to be at least 2% and may spike in the period. The inflation goes to principal as reflected in the bond adjustment factor, and you get BAF x $1000 per bond at maturity.
Disadvantages are it is out a year plus to maturity, and you need to put at least $100K in at a pop. Also, beware purchase price is adjusted to include the bond adjustment factor (where the inflation went before and goes in the future). This is 1.16535 on this one now, but of course you get paid it back, plus future inflation, at maturity. So one of these bonds really cost $1.165 x $1000.665. Also you get taxed on the inflation interest although you receive no cash, so that is a consideration in taxable accounts.
Needless to say, liquidity is not a problem. A round lot is really $1 million face, but you don't get screwed on the $100K order, unlike some bonds.
Call me paranoid, but in a real panic I want real U.S. Treasury paper, not a fund, not a bank, not nothing else. They would be the last man standing. You get a comparable yield (and no state tax, if you care) so I go for these.
XFC's expectation of bad economic times and worse for the markets seems apt. All things must pass.