Maybank — Fraud Triage

Maybank's fraud team runs a simple rule: flag any account with several large transactions in a short burst. That rule alone over-flags — a small business paying three supplier invoices back-to-back looks identical to a stolen card being tested across sites. Five steps: filter to large transactions, self-join to find rapid-fire pairs, list the flagged accounts, separate real fraud from the look-alike with a merchant-diversity check, then count who actually gets escalated.

Schema

▸maybank_transactions

transaction_id	SERIAL
account_id	INT
txn_time	TIMESTAMP
amount	NUMERIC(10,2)
merchant_category	TEXT

5 steps

1Filter to large transactions
2Self-join to find rapid-fire large transactions
3List accounts with at least one velocity pair
4Separate real fraud from false positives with a merchant-diversity check
5Count the accounts to actually escalate

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