Moving value inside a system.
WHAT MAKES IT ATTRACTIVE
Instant, free or cheap, and entirely within your control.
WHAT IT REQUIRES
Reliable identification of the recipient Confirmation before sending Atomic movement between balances
WHAT ATOMIC MEANS
Both sides succeed or neither does.
WHY THAT IS NON-NEGOTIABLE
A debit without a credit destroys money; a credit without a debit creates it.
WHAT TO ENFORCE
The transfer as a single database transaction, or with compensating entries.
WHAT TO DISPLAY BEFORE CONFIRMATION
The recipient's name, the amount, and any fee.
WHY THE NAME
It is the only defence against sending to the wrong person.
WHAT TO HANDLE
Insufficient balance Recipient account closed or restricted Concurrent transfers from the same balance
WHY THAT LAST POINT
Two simultaneous transfers can both pass a balance check and overdraw.
WHAT PREVENTS IT
Locking, or a constraint preventing a negative balance.
WHAT TO MONITOR
Transfers immediately followed by withdrawal Many small transfers into one account Accounts receiving from many unrelated senders
WHY
Those are laundering patterns.
WHAT TO NEVER ALLOW
Reversal of a completed transfer without a defined process.
