A daily task list that resets cleanly
Generate the day's tasks once, track progress against a date key, and pay the completion bonus exactly once — no midnight cron required.
Tagged “ledger”
10 entries
Achievements that reward the behaviour you want
A table of conditions, a checker that runs after activity, and a unique key so an achievement can only be awarded once.
Three referral commission models, and what each one costs
Percentage of earnings, one-off signup bonus, or a share of what you earn from the referral. The arithmetic that decides which one bankrupts you.
Adjust a member's balance without losing the trail
Every manual adjustment writes a ledger row and an audit row, inside one transaction. An admin panel that edits a balance directly is how books stop balancing.
Minimum withdrawals and fees, driven by settings
Compute the fee once, show the net before they confirm, and keep every threshold in the settings table so repricing is not a code change.
Guard against a negative balance, and claw back correctly
Make the column unsigned, check inside the transaction, and let a clawback take a balance to zero rather than below it.
Idempotency keys on every operation that moves money
A caller-supplied key with a unique index turns every retry, refresh and double-click into a no-op. The single most valuable column in a payments schema.
Credit a deposit exactly once, however many callbacks arrive
A unique index on your own reference turns duplicate callbacks, browser refreshes and manual replays into no-ops instead of free balance.
A withdrawal that cannot be paid twice
Debit on request, not on approval. The state machine that makes double payouts and phantom balances impossible.
Move balance between two accounts without losing any
Lock both rows in a fixed order, check inside the transaction, and write a ledger entry for each side. Skipping any of the three is how balances drift.