Quick answer: Model virtual currency as an append-only ledger of transactions from which balances are derived, so every change is traceable and balances reconcile.
A currency balance with no ledger is impossible to audit. A ledger makes every change traceable. Here is how.
How to fix it
1. Record transactions, not just balances
Append every credit and debit as a ledger entry.
2. Derive balances
Compute balances from the ledger so they always reconcile.
3. Make it immutable
Keep the ledger append-only so history is trustworthy for audits.
Catching the ones you can't reproduce
The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.
Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.
This is where a tool like Bugnet earns its place. Its SDK captures every backend error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.
The bug you can't reproduce isn't gone — it's just invisible until you capture it from the player's device.