I’m trying to manage an shared account balance that can be acessed by multiple users, for this I need sequencial transactions to assure actual state. It’s my first prod ready project so probably won’t have many acess, probably would be possible to store the balance on a json based file. Anyway, what approaches could I use to assure that? Ecto has fragments and some lock features, but by the docs sounds like cryptics and with a lot of contraints instead of just plug or run a manual query. I was thinking on a genserver with a variable controlling whether the process is acessing the db or not, similar to a singleton. Would that be viable? what other ways could I do it?