Dashboard
0%
1
Curious builder0 XP earned · 300 to level 2
0 daysFinish a lesson to begin
Badge collection0 of 6 unlocked
51 small wins to finish your pathNext question →

Q40HardSystem design

Design a system where a fraud-detection ML model flags transactions and an LLM helps investigators understand and resolve cases.

30-second answerSay your answer out loud first, then reveal.
Transactions flow through a feature store into a fast fraud model that approves, blocks or creates a case; an investigation copilot calls tools for history, device, SHAP attributions and similar cases, writes a case summary, and the investigator decides, with labels feeding retraining.

Why this split

  • Real-time scoring needs millisecond latency at massive volume, plus calibrated, auditable scores. Classical ML fits this.
  • Investigations involve reading heterogeneous evidence and writing narratives. LLMs fit this and save investigator time.

Copilot design details

  • Structured output: timeline, risk indicators, each with a source reference (record IDs).
  • Faithfulness: numbers are pulled by tools and rendered by code, not generated by the LLM. Every claim links to evidence.
  • Explanations: convert model attributions (SHAP) into plain language: "Flagged mainly due to a new device + transaction amount 12x the customer's average + high-risk merchant category."
  • Compliance: draft SAR/STR narratives for human review; full audit logs; data access restricted by role.
  • Security: treat transaction descriptions and merchant names as untrusted (prompt injection risk).

Metrics: investigation time per case, decision accuracy (vs QA review), backlog size, investigator satisfaction, false positive handling time.

Every expert started right here.