Multi-currency finance core
Every monetary row stores native amount + native currency + an FxRateSnapshot foreign key. Reports compute against the snapshot, never live FX.
in production, no sandbox here
This one runs in Beeline Medical. It has no sandbox on this site, because the pattern only means anything against a real database, real roles, and real money. Rebuilding that as a toy would demonstrate the toy.
The write-up covers how it works and where it is deployed.