Define Success Metrics for a Social Feed Feature

You are evaluating a change to the main social feed in a large-scale consumer app. Assume events are logged to a single analytics table with impression-level and action-level events.

Minimal events table (to ground definitions):

• user_id, session_id, event_time (UTC), tz_offset_min
• event_type ∈ {feed_load, impression, like, comment, share, save, hide, report, follow, unfollow, crash}
• impression_id, content_id, creator_id
• dwell_ms (on impression), server_latency_ms (on feed_load)
• device_integrity ∈ {PASS, FAIL}, bot_score ∈ [0,1]

Specify:

(a) The primary success metric(s) with exact formulas (numerator/denominator and units).

(b) Guardrail metrics (e.g., latency, content quality, reliability) with formulas and units.

(c) The eligible population and unit of analysis (e.g., user-day, session, impression) for the primary metric and guardrails.

(d) Data hygiene rules: how to handle bots, empty sessions, outliers, and time zones.

(e) How each metric would be computed from the events table (outline the steps and any key joins/windowing).

Finally, discuss the trade-offs between engagement, quality, and reliability, and how your metric set balances these.