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Design a Fitness Activity Tracking App with Followers and Leaderboards

Fuse EnergySoftware Engineer · Onsite
MediumSoftware EngineerOnsiteSystem Design

Last updated

Prepare for a Fuse Energy system design interview about design a fitness activity tracking app with followers and leaderboards. This question focuses on requirements, architecture, trade-offs, reliability, and follow-up discussion areas.

Design a fitness activity tracking app where followers can see current trails, users can query top activities by time range, and leaderboards are supported.

Constraints & Assumptions

  • Preserve the source scope; do not assume extra company-specific systems.
  • Focus on interview reasoning, correctness, and operational trade-offs.
  • Explain how you would validate the answer with examples, metrics, or tests.

Clarifying Questions to Ask

  • What exact user, system, or business goal should this solve?
  • What scale, latency, reliability, or privacy constraint matters most?
  • What existing infrastructure or code must the solution integrate with?
  • What output or behavior will the interviewer use to judge success?

Hints

Hint 1

Hint 1: Start by stating assumptions, then work from requirements to trade-offs and validation.

Hint 2

Hint 2: Use concrete examples from the prompt and make edge cases explicit.

Follow-up questions

  • How would your answer change at 10x scale?
  • What would you monitor in production?
  • What edge case is easiest to miss?
  • What would you simplify if this were a 60-minute implementation round?