I think I've used flyweight in exactly one production system, and it was a trading system. Lots of transactions (easily tens or hundred of millions in a given d

I think I've used flyweight in exactly one production system, and it was a trading system. Lots of transactions (easily tens or hundred of millions in a given day in a single process), lots of duplicated instrument data. Perfect use case for flyweight. But, yeah. It's a fairly rare use case. Good to know about, but not necessarily one you need to keep fresh in mind, ready for use.