The Bitcoin blockchain processes a block of transactions every 10 minutes on average. Each block usually contains 2k-4k transactions. The maximum capacity is around 4k, equating to 7 transactions per second or 84 transactions per 12 seconds. (Note that 12 seconds is the confirmation time of the Ethereum blockchain).

That being said, the Lightning Network was deployed on the Bitcoin blockchain in 2018. It allows for thousands of transactions per second, thanks to a very elegant solution[1]. Unlike traditional blockchains, the Lightning Network is not blockchain-based, freeing it from the limitations we are all familiar with. However, it inherits all the security properties of its underlying blockchain. While the Lightning Network has its fair share of shortcomings, its scalability remains an open question. Nonetheless, it has been working great for over 5 years.

[1] https://lightning.network/lightning-network-paper.pdf

(Most) trading's not done on chain, it's settled later. Alameda could absolutely trade faster than that.

Doesn’t that just mean the trading is done by a trusted third party? Fine until the third party goes belly up.

This is how most asset trading works, but outside of crypto these third parties are actually trustworthy

Well, one might argue they’re trusted to grift retail. The money firms make doesn’t come out of thin air. SEC is fairly toothless in this area.

> outside of crypto these third parties are actually trustworthy

With multiple layers of mutualised failsafes.

Don't forget meaningful regulations and legal requirements placed upon these parties

Yes, the exchanges are 3rd parties that could lose, and often do lose, the money

I thought the (noncrypto) financial exchanges made a very small amount of money on every trade.

Has this improved as of late? Maybe with other blockchain systems?

Yes, it improved in 2018, but people are still stuck on the 12 tx/s. The Lightning network allows thousands of tx per second [1].

[1] https://en.wikipedia.org/wiki/Lightning_Network

Snarky (flamewar starting) answer is it improved massively since they made the blocks bigger in 2017.