Comment by the_local_host

This seems to good to be true. From https://money-legos.studydefi.com/#/dydx :

    Borrow x amount of tokens. (Withdraw)
    Call a function (i.e. Logic to handle flashloaned funds). (Call)
    Deposit back x (+2 wei) amount of tokens. (Deposit)

It looks like unlimited leverage for flat fee.