Question

Design the accounting subsystem that produces a daily trial balance and supports month-end close for a fintech with ~30M ledger entries/day across a configurable chart of accounts. The trial balance (sum of all debits == sum of all credits, per account) must be queryable on demand, and once a period is closed its entries must be frozen — late transactions go to the next open period. Describe the model, how you compute the trial balance efficiently, and how you enforce period-close immutability.