PM Technical: Sketch the Backend Architecture Behind Strava's Activity Tracking
Company: Google
Role: Product Manager
Category: System Design
Difficulty: medium
Interview Round: Other
As a product manager, you are asked a technical question: how do the systems behind Strava work? Strava is a fitness app where people record runs, rides and other workouts with a phone or a wearable, look at their stats, share activities with people who follow them, and compare their times with others. Describe the main components at a high level, trace how one workout moves from being recorded to showing up for friends, and discuss the key design trade-offs.
```hint Follow one workout
Trace a single workout from the moment it is recorded on a phone or watch, through upload and processing, to the athlete's own view and their followers' feeds. Each hop points to a component and a design decision.
```
### Clarifying Questions
- Should the answer cover only the core loop (record, upload, process, view, share, compare), or also route planning, subscriptions and heatmaps?
- Do workouts arrive only from the phone app, or also from third-party watches and bike computers that sync files?
- How deep should the answer go: a block diagram with data flows, or specific storage and scaling choices?
- Which comparison feature matters most: the follower feed, leaderboards on popular stretches of road or trail, or personal records?
### What a Strong Answer Covers
- The core user journey and the entities it implies: athlete, activity, GPS stream, segment, follow relationship and leaderboard entry.
- Ingestion from phones and wearables, including offline recording and asynchronous processing of uploaded files.
- Storage that separates small metadata from large GPS time series, and how stats and segment efforts are computed.
- The social read path, a follower feed and leaderboards, with the trade-off between doing work at write time and at read time.
- Location privacy, scaling and failure handling, explained at a level a product manager can defend.
### Follow-up Questions
- A popular race finishes and 50,000 people upload within an hour. Where does the system strain, and what would you change?
- How would you hide the start and end of activities near a user's home without breaking leaderboard results?
- A user reports a leaderboard time that is impossibly fast. How should the system detect and handle it?
Overview: A technical question for product managers about how the systems behind Strava could work. It tests explaining the path of a workout from phone or wearable upload through processing, storage, segment leaderboards and follower feeds, along with location privacy, scaling and the trade-offs a PM should be able to discuss.