Nice article, I'd be curious to know if/how their engine abstracts the complexity behind multi-currency transactions, or whether they rely on the accounting model to handle multi-currency.

We built our own double-entry accounting engine at my previous company, and while the engine was not as fancy as what Square describes, the real challenge was building out the accounting models that manipulated the engine's primitives.

To this day, I have yet to find another resource on multi-currency that is as solid as this one:

https://www.mathstat.dal.ca/~selinger/accounting/tutorial.ht...