I just noticed how much the Fidelity Core "Gov't" yields have slipped.
My Cores (FDRXX in IRAs and FZFXX in Trust) are yielding .01%. Tomorrow they go into my Prime MM Core Back-ups (FZDXX in IRAs and SPRXX in Trust) which are yielding .43% and .31%, respectively.
To avoid being trapped by prime m-mkt gates and/or redemption, keep enough in gov m-mkt core for possible near-term trades/needs.
After using T-Bills last year, and short-term brokered-CDs earlier this year [they have to pay 0.25-0.50% broker platform fee, so their rates are too low now], I am now just using short/intermediate/limited-term bond funds [investment-grade] for parking cash. Beware that there aren't M* ST-core and ST-core-plus categories for ST bond funds, so one has to look at individual fund objectives and portfolios.
Chasing online savings accounts isn't practical for me as for a trust account, I have to use paper forms to open new accounts - no online account opening. I do have one but its rate is not good now. The firm keeps offering new and better rate accounts but requires old account closing and new account opening each time.
Good advice YBB. In my case, I have an Automatic Investment Program (AIP) draw set up for late July into one of the ST funds you mention. So it is easier for me right now to simply move most of Core to Core Back-up. Fidelity will automatically use my Core Back-up for any purchases I decide to make, except that when the July AIP comes around I need to move sufficient funds back into Core as Fidelity requires all the AIP money be in the Core. The way I do that is simply sell sufficient amount of Core Back-up a few days ahead of the AIP and the cash proceeds of sale will accumulate in Core.