Practice real data science interviews tuned by the interviewers who actually run them.

Facebook's News Feed team shipped a ranking algorithm change last week. Since then, comments per user are down 12% but time spent is up 5%. The VP wants to know: is this a problem?

Facebook is considering removing visible like counts from posts. Instagram already tested hiding likes in several markets. You need to think through how to measure the full impact of this change across users, creators, and the platform ecosystem.

The Facebook Newsfeed team is trying to understand whether users see enough friend content in their feed. The balance between friend posts, public content, and recommended content is critical to Facebook's value proposition. You need to figure out how to measure and optimize this.

The Reels team has flagged an alarming trend: 'average reels watched per session' has dropped precipitously over the past week. The VP wants answers by end of day. You need to diagnose what's happening and whether it's actually a problem.

Amazon's return rate jumped 15% week-over-week. The VP of Customer Experience wants answers by end of day. Walk me through your investigation.

YouTube's total watch time dropped 8% week-over-week. The VP of Product wants a root cause analysis before the quarterly business review. Multiple platform, regional, and content-type dimensions may be driving the decline, and early data suggests the drop is concentrated on mobile.

Google Play's privacy perception score improved 8% after launching prominent privacy labels, but Play Store engagement (app installs, browse time, return visits) dropped 14% in the same period. The VP of Trust & Safety wants to understand whether the privacy initiative is hurting engagement or if this is coincidental.

Average searches per user declined 4% globally, but average searches per user increased in every individual country. The CEO asks why the global number is going down if every country is improving. You need to diagnose and explain this paradox clearly enough for an executive audience.

Google Maps DAU dropped 10% over the past 2 weeks. The VP of Geo wants an explanation before the exec review. The drop could stem from a recent iOS update, a product change, an external factor, or a data quality issue. You need to systematically rule out hypotheses.

Rider cancellation rate in San Francisco jumped from 8% to 14% over the last week. Your team flagged this. Walk me through your investigation.

TikTok's recommendation team optimized for watch-through rate instead of engagement rate. Watch time is up 5%, but creator follower growth is down 8%. The creator partnerships team is concerned. Investigate.

Coinbase's total trading volume dropped 30% month-over-month. The CEO wants to understand if this is a market problem or a product problem. Walk through your investigation.

Cold food complaints have spiked 34% over the past 3 weeks across 12 metro areas. The VP of Customer Experience wants a root cause analysis. Two recent operational changes — batched delivery and prep time inflation — may be interacting in unexpected ways.

Average delivery time increased by 4.2 minutes last month across the platform. No major product changes were shipped. The operations team is alarmed and wants to know what's driving the increase and whether it requires immediate action.

Consumer order cancellations are up 28% in specific geographic markets over the past two weeks. The pattern is concentrated in suburban areas during dinner rush hours. You need to diagnose the root cause and recommend immediate actions.

Spotify's app installs dropped 25% month-over-month across all platforms. The CMO flagged this in the weekly business review and wants a root cause analysis within 48 hours. Multiple factors could be at play — marketing spend changes, competitive moves, platform-level shifts, and seasonality. You need to structure the investigation, identify the most likely causes, and size their impact.

Spotify's Trust & Safety team has flagged a spike in anomalous account behavior — accounts with listening patterns consistent with credential sharing, bot-driven stream farming, or compromised accounts. These accounts inflate streaming metrics, distort royalty payouts, and degrade recommendation quality. You need to design signals for detecting different types of anomalous behavior, set appropriate thresholds, reason about false positive tolerance, and define success metrics for a fraud detection system.

Netflix's primary engagement metric has dropped 20% week-over-week. Leadership is alarmed and wants a root cause analysis within 48 hours. The drop could be a data issue, a seasonal effect, a product change, a content gap, or a genuine shift in user behavior. You need to structure a systematic investigation and determine what's real vs. artifactual.