Design a fraud detection system
Hard45 minFree, no account
One in a thousand positives, an adversary who adapts, and a false positive that costs a customer.
The question
Design real-time fraud detection for card payments: approve, decline, or send for review, in under 200ms.
About 0.1% of transactions are fraudulent.
Functional
- Score every transaction before authorisation.
- Three outcomes: approve, decline, hold for manual review.
- Explain any decline to an analyst.
Non-functional
- 200ms budget including feature lookup.
- The adversary adapts within days.
- A false decline costs a customer; a false approve costs money.
45:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.
Stuck?
0 of 3 hints takenThe worked solution
written by a person · not a gradeScore yourself
0 of 5 marked- Rejected accuracy and expressed the trade in money25
- Three outcomes with a deliberate step-up band20
- Streaming velocity and graph features, with the latency budget respected20
- Named training-serving skew and how to prevent it15
- Handled delayed and censored labels, and adversarial drift20
We run no AI here and nothing on this page grades you. The score is yours, and the useful number is the one you get on the same problem a month from now, cold.
kept in this browser only