Root-Causing a Monthly Active User Decline on a Meta App
Company: Meta
Role: Product Manager
Category: Analytics & Experimentation
Difficulty: medium
Interview Round: Other
You are a PM at Meta and see that monthly active users (MAU) for your product are down this month. How would you work out what is behind the decline, and what would you do next?
```hint Pin down when and where
Before brainstorming causes, find out whether the decline is a step on one day or a gradual slide, and which users it is concentrated in. Those two facts rule out more causes than any checklist.
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### Clarifying Questions
- Which product is it: Facebook, Instagram, WhatsApp, Messenger, or the count across all of Meta's apps?
- Is MAU counted per calendar month or over a rolling window, and which action makes a user count as active?
- Down compared with what (last month, the same month last year, or the forecast), and by how much?
- Is the drop global, or concentrated in particular regions or platforms?
### What a Strong Answer Covers
- Confirming the drop is real: the metric definition, the comparison baseline, calendar effects, and logging or pipeline changes.
- Narrowing the decline by its timing and by segment (region, platform, app version, new versus existing users).
- Breaking MAU into new, retained and returning users to see which flow changed.
- A ranked set of internal and external hypotheses, each paired with the data that would confirm or rule it out.
- Turning the cause into action: sizing it, fixing or rolling back, communicating, and judging whether the drop matters.
### Follow-up Questions
- The decline turns out to be almost entirely among returning Android users. What do you check next?
- Daily active users held steady while MAU fell. What does that tell you?
- Leadership wants to launch a re-engagement push right away. What do you advise?
Overview: A metric diagnosis prompt about a drop in monthly active users on a Meta app. It tests whether a PM can validate the metric, narrow the decline by timing and segment, separate internal from external causes, and turn the finding into a concrete plan of action.