Comment by latchkey

Front running a transaction is essentially a sandwich attack. It primarily happens in illiquid markets where someone sees a transaction in the mempool, does a large flash loan borrow to affect prices, then your transaction executes at a poor price point, and the loan is paid off. All in a single block. 1) Typical transactions are not front run. 2) There are ways of preventing front-running. This is not really an issue for the majority of users or a design flaw.

> you know the exchange rate before you trigger the exchange

You know this in crypto too. The issue is that the market depth might not be large enough to support your transaction. That will change over time, or you just stick with the basics... BTC/ETH/Stables and ignore the rest of the stuff.

> how does immutability facilitate this?

If you know that it is impossible to double spend, you can trust the math.

> And how is a blockchain that can technically be rewritten at non-infinite cost immutable

This is well covered in Andreas Antonopoulos videos on YT.

> Credit cards (and payday loans) exist for people who lack the collateral for a non-signature loan.

In Vietnam, there is no credit reporting agency. You don't get a credit card from a bank, but you can get a MasterCard/Visa "credit card". The thing is, they are effectively debit cards because you have to time deposit collateral in order to use them. People still get to shop online, but they are limited. This is honestly a far better system because it encourages people to spend what they have, not what they don't have. I also prefer to cut out the middleman who's generating all those fees for both the merchants and the end users.

> The only way to do this in crypto is to trust a third party lender such as Voyager or Celsius.

Bad examples given that Celsius was a ponzi. There are decentralized lending protocols. AAVE is a good example.