<aside> 💡 Solution

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Note: This document links directly to relevant areas found in the system design topics to avoid duplication. Refer to the linked content for general talking points, tradeoffs, and alternatives.

Step 1: Outline use cases and constraints

Gather requirements and scope the problem. Ask questions to clarify use cases and constraints. Discuss assumptions.

Without an interviewer to address clarifying questions, we'll define some use cases and constraints.

Use cases

We'll scope the problem to handle only the following use cases

• User searches for someone and sees the shortest path to the searched person
• Service has high availability

Constraints and assumptions

State assumptions

• Traffic is not evenly distributed
  • Some searches are more popular than others, while others are only executed once
• Graph data won't fit on a single machine
• Graph edges are unweighted
• 100 million users
• 50 friends per user average
• 1 billion friend searches per month

Exercise the use of more traditional systems - don't use graph-specific solutions such as GraphQL or a graph database like Neo4j

Calculate usage

Clarify with your interviewer if you should run back-of-the-envelope usage calculations.