So where do you keep that more than $3M in cash? Always in N/250k banks? This is not a useful solution to running a company.

I mentioned in another comment, but there are account features where your money is deposited to N banks automatically. i.e.

https://www.interactivebrokers.com/en/accounts/sweep-program...

https://www.cnb.com/business-banking/accounts/savings/bank-d...

https://www.wellsfargo.com/investing/cash-sweep/

Of course if those banks are depositing to the same 10 banks then you're really protected at 10x...but, well much better than 250k? I'm going to guess it's called a "Sweep Program" but I'm no finance expert. I know of this because it's common for brokerage account to do this - as very often, you'll have more than $250k in cash if you're doing active trading.

You just ask IntraFi to place it for you. https://www.intrafi.com/services/deposit-solutions/for-regio...

It generally looks transparent and like it's just in your chosen bank. (Though if you want laddering, etc, you do need to plan).

If you have a lot of cash, you buy T-Bills and other instruments with some of it.

And yes, you have some risk remaining, of some of the cash disappearing. But with diversification and insurance, it is negligible.