Business Context

You are an Engineering Manager supporting Facebook Groups. Leadership is deciding whether to invest the next two quarters in recommendation quality, notification reliability, or group admin tooling. They want a data-driven framework for making management decisions rather than relying on anecdotal feedback from a few large communities.

Metric Scenario

Facebook Groups has 210M weekly active members and 12M monthly active groups. In the last quarter, weekly active members grew 4%, but 7-day retention for new joiners fell from 41% to 36%. At the same time, posts per active group rose 9%, while meaningful interactions per member (comments + reactions + shares on viewed group content) increased only 1%. Notification delivery success is 98.7% overall, but only 93.8% on Android in India. Group admin actions per week are up 15%, and reports of spam posts are up 11%.

The VP of Product asks: "How should data inform where we invest engineering capacity, and which metrics should we use to decide?"

Requirements

1. Define a primary KPI for Facebook Groups that is useful for management decisions.
2. Identify 3-5 supporting metrics, including leading and lagging indicators.
3. Explain how you would decompose the KPI to diagnose the retention decline.
4. Recommend which engineering area you would prioritize first using the data above.
5. Describe what guardrails you would monitor to avoid improving one metric while harming the product.

Data Available

• group_membership_events
• group_content_events
• notification_delivery_logs
• group_admin_actions
• integrity_reports
• user_sessions