I don't work at Stripe, but I've talked to a few ledger nerds there.
One thing I'd point out that makes Stripe's ledger different than most others you might have seen or encountered is the granularity of what they consider an account. If you think about a bank ledger, you logically have a single account per customer. Stripe uses multiple accounts for each payment, so processing this number of accounts is a hard scaling problem, especially when most are ephemeral. The saving grace is that this can be done offline and balances can be eventually consistent or materialised on read.
When you have this many accounts, organising them also is a big challenge, since you want to be able to roll them up to something meaningful. Conceptually asset and liability accounts in a ledger represent a financial relationship with an economic actor. If that's the top level account (e.g. how much does bank X owe us right now) you'll want to have a hierarchy of accounts down to each state of each payment. So a lot of effort went into building modelling tools for product teams to design how their financial activity gets represented in the ledger.
Disclaimer: I'm CTO at Fragment (http://fragment.dev) and Stripe led our last round.