You're a fintech wallet without a banking license. Your users' funds sit in an 'For Benefit Of' (FBO) account at your sponsor bank. From the sponsor's view: ONE bulk deposit. From yours: many user wallets, summing to that same total. The invariant you MUST maintain forever: sum(user wallets) = FBO balance. If they ever disagree, you're either commingling, you have a bug, or you've been robbed. This is THE foundational pattern for any unlicensed fintech that holds user money.