Users also can borrow from USDC or USDT pool and pay interest for doing so. Below are the stable and variable borrowing rate for USDC and USDT. We can see that the rate has settled down and remain constant from end May to now.

Users can earn interest when they deposited (aka lending) their USDC and USDT into Aave Market. Below are the historical APY earned by users.

The top 2 stablecoins deposited on AAVE are USDC and USDT as per graph below.