Business Context

Instagram is evaluating whether the Save button creates meaningful long-term value or just adds lightweight engagement. Over the last quarter, product leadership noted that Save taps increased from 2.8% to 3.6% of feed impressions, but overall 7-day retention stayed flat at 41% and daily sessions per user rose only 1%.

Metric Scenario

The team wants a clear framework to measure the success of the Save button for Feed posts, Reels, and Explore content. They are specifically asking whether Save is a strong signal of user value, whether it drives return behavior, and how to distinguish “accidental taps” from intentional bookmarking. Current data shows 18M daily Save events, 11M unique savers/day, 62% of saved posts are never revisited within 30 days, and users who save at least one item per week have 1.8x higher 30-day retention than users who never save. However, this correlation may be confounded by power-user behavior.

Requirements

1. Define the primary success metric for the Save button and explain why it is the right KPI.
2. Propose 3-5 supporting metrics and guardrails to evaluate quality, engagement, and retention impact.
3. Describe how you would decompose the metric to diagnose whether Save is working better for certain surfaces, content types, or user segments.
4. Explain how you would determine whether Save causes higher retention versus simply correlates with already engaged users.
5. Recommend what decision you would make if Save rate rises but revisit rate and retention do not.

Data Available

• save_events: user_id, content_id, creator_id, surface, timestamp
• content_impressions: user_id, content_id, surface, position, timestamp
• content_revisits: user_id, content_id, revisit_timestamp, source
• user_sessions: user_id, session_id, session_start, session_end, app_version
• user_profile: user_id, signup_date, country, device_type, account_age_days