I briefly dabbled in financial ledgers in a previous job. We made plans to do what you seem to be describing, which is to store the transactions themselves and calculate a balance as needed, but we frankly lacked expertise. I always wondered what would happen if we scaled to millions of transactions in that system.

Is there a standard strategy for optimizing balance queries against a series of transactions? I assumed that we would eventually have to cache some kind of snapshot for each account to avoid the overhead of totaling every transaction on every balance check.