What is the difference between a Tree and a Graph?

0-2 years experience

1. 1We need to store a company's org chart where each employee has exactly one manager. Would you model this as a tree or a graph, and why?
2. 2If you have a binary heap implementation and you accidentally add an edge that creates a cycle, what issues would arise during heap operations?

2-5 years experience

1. 1Our feature builds a dependency resolver that must detect circular dependencies. How would you use graph vs tree concepts to implement this, and what pitfalls might cause it to break?
2. 2We migrated a file system hierarchy from a tree representation to a graph to support hard links. What changes in traversal algorithms and edge cases do you need to consider?

5-8 years experience

1. 1Design a service that stores and queries hierarchical categories but also allows cross‑category relationships (e.g., product recommendations). How would you decide when to use a tree structure versus a general graph, and what performance trade‑offs does each bring at scale?
2. 2Our recommendation engine currently uses a tree for user interests, but we see users with multiple overlapping interests causing duplication. How would you refactor the data model to a graph, and what impact does that have on query latency and consistency?

8+ years experience

1. 1Across multiple teams we have legacy data stored as adjacency lists for a graph, but a new analytics platform expects a tree‑like hierarchy. How would you plan a migration strategy that minimizes downtime and ensures both systems can coexist during the transition?
2. 2When building a global permission system, you must decide between a tree (role inheritance) and a directed acyclic graph (multiple inheritance). What architectural considerations, such as security audits and policy evaluation performance, drive your choice, and how would you future‑proof the design?