BehavioralEmbracing AmbiguityBuilt on CRAFT

Describe a project where the goalposts kept moving and you had to repeatedly adapt your approach.

Senior+Platform architectureAdversarial systems

Behavioral rounds at FAANG and AI labs now include 1-2 design follow-ups. Each answer below ships with both.

CContext

The situation, your role, and the stakes, compressed.

A fraud detection LSTM project at an ad-tech company started with one goal: detect fraudulent PII in leads. Every 2-3 weeks the requirements shifted: also detect bot traffic, then real-time not batch, then explainability for legal compliance, then 5 client integrations with different data formats. Meanwhile fraud patterns kept evolving and I was getting alerts at 2 AM about new attack vectors.

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Design Follow-Ups

The new behavioral round

Behavioral rounds increasingly drop into 1-2 technical follow-ups that probe whether you could actually build the system you described. These are the design questions a real interviewer would ask after this STAR answer.

1

Walk through the three-layer architecture in detail. How do the swappable models compose, and what's the contract between layers?

2

Streaming inference at 100ms p99 with an LSTM in the loop is non-trivial. Design that.