Yeah, the example is not representative - in reality there's a couple of smaller vectors (base prices, meal prices, supplements, discounts, taxes, cancellation policies, ...) + lots of vectors containing indices (`for 2018-01-01, match prices #10, #20, #21`, `for 2018-01-02, match prices #11, #30`, ...), and they can't be actually updated in-place, because that would require using `RwLock`, preventing the engine from answering queries during refreshing.

(which is actually how it used to work a couple of years ago - ditching `RwLock` for `ArcSwap` and making the entire engine atomic was one of the coolest changes I've implemented here, probably worth its own post)