Responding to Complaints of a Sluggish Mobile App: Diagnosis, Fixes and Prevention
Company: Zillow
Role: Product Manager
Category: Analytics & Experimentation
Difficulty: medium
Interview Round: Other
Users of your mobile app are complaining that it is slow. As the product manager, what would you do? Walk through how you would work out what is happening, how you would respond, and how you would keep it from happening again.
```hint Confirm and locate before fixing
Before choosing a fix, check whether your own measurements show the slowdown, and find where it is concentrated: which screens or actions, which users, and since when.
```
### Clarifying Questions
- How many users are complaining, through which channels (app-store reviews, support tickets, social media), and since when? Did it start suddenly or build up gradually?
- Is the whole app slow, or particular actions such as launching the app, searching, scrolling or loading images?
- Is it limited to certain platforms, devices, app versions, regions or network types?
- Do we already collect performance data such as screen load times and server response times, or do we mostly learn about problems from complaints?
### What a Strong Answer Covers
- Checking the complaints against performance data before acting, with "slow" defined in measurable terms.
- Narrowing the problem down by action, platform, app version, device, network, region and start time.
- Internal and external causes considered in a sensible order, each with the evidence that would confirm or rule it out.
- An immediate response, including mitigation and communication with users, kept separate from the root-cause fix, with the trade-offs between them.
- Prevention: performance targets, monitoring, alerts and release safeguards so the team finds out before users complain.
### Follow-up Questions
- Your data shows no change in load times, yet complaints keep rising. What could explain that, and what would you do?
- The slowdown comes from a new feature that is increasing engagement. How would you decide between turning it off and keeping it while engineering optimizes it?
- Which performance metrics would you put on the team's dashboard, and how would you set alert thresholds?
Overview: A product analytics interview question in which mobile app users complain that the app is slow and the product manager must decide what to do. It tests validating complaints with performance data, isolating where the slowdown occurs, ranking likely causes, responding quickly and preventing repeats.