Break the problem into two CTEs: one for qualifying logins (first successful login from a new device/IP in the prior 30 days, excluding accounts <7 days old) and one for qualifying transfers (>$500 to a first-time recipient within 2 hours of login). Join them on user_id with a time window, deduplicate to keep the earliest transfer per login, and assign a reason code. Finally, recommend indexes on the join and filter columns to optimize performance.
Pro tip: Explicitly state your assumptions about 'first-time recipient' (e.g., no prior transfers to that recipient in the last 30 days) and 'new device/IP' (e.g., not seen in the user's history in the prior 30 days), as these definitions can vary. Also, mention that you would validate the query with a small sample and consider edge cases like timezone handling and NULL values.
Create a CTE that selects successful logins in the last 7 days where the device_id and ip_address are new for the user in the prior 30 days, and the account is at least 7 days old at login time.
Create a CTE that selects transfers over $500 to a recipient not previously sent to by the user (first-time recipient), along with the transfer timestamp and recipient_id.
Join the qualifying logins and transfers on user_id where the transfer occurs within 2 hours after the login. Use a window function to rank transfers per login by transfer time and keep only the earliest.
Select the required columns (e.g., user_id, login_time, transfer_time, device_id, ip_address, amount, recipient_id) and add a reason code like 'ACCOUNT_TAKEOVER' or 'NEW_DEVICE_NEW_IP_TRANSFER'.
Suggest indexes on login_events(user_id, login_time, success, device_id, ip_address) and transfers(user_id, transfer_time, amount, recipient_id) to speed up filtering and joins.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.