I bonds are meant to protect investors from inflation, and they have a fixed interest rate that reflects the inflationary environment. They typically don’t get much attention, but with a dropping market and soaring cost-of-living, they gained popularity over the past few months thanks to the 9.26% interest rate, becoming one of the best performing investments available.

TreasuryDirect.gov is the only website where investors can directly purchase those securities. This week, it became one of the most visited federal sites on the web, officials said, as investors rushed to secure the deal in an otherwise shaky and unstable financial environment. The site has occasionally been inaccessible due to the unprecedented traffic.

Investors need to complete their purchase and receive a confirmation email by 11:59:59 p.m. ET on Oct. 28 to receive the 9.62% rate, which is then locked in for six months.

“Due to high volumes, we cannot guarantee that your bond purchase will be completed before this deadline if your account or purchase requires additional customer support for issues such as identity verification,” the Treasury site reads.

If the bonds are purchased after that 11:59 p.m. deadline, they will receive the November rate. That new rate will be set on Nov. 1, and is expected to be significantly lower.

Treasury issued $1.95 billion in I bonds during the last week of October—that’s twice as much as during all of fiscal year 2021, according to the department. And in the past year, about 3.7 million accounts were created on TreasuryDirect.gov, more than in the last 10 years combined.

To buy the bonds, investors need to create an account on TreasuryDirect.gov. That could slow down the process, depending on the user. Investors can buy $10,000 worth of electronic I bonds per person annually. They earn interest for 30 years—the rate changes every six months—unless you redeem them early. Technically, you can cash them out after 12 months, but doing so will cost you three months’ worth of interest.