So this is totally a US financial thing but the IT folks will get a kick out of this...
The website to buy I bonds is prehistoric, like GeoCities old, but up until 2020 Treasury Direct only sold $350M bonds in a year. The website was janky but serviceable. Since these bonds are tied to inflation the rate has gone up a lot in the last 12 months, TD has sold almost $30B in 11 months. The last day to buy these and get the current 9% rate is tomorrow at midnight.