Hardest Senior React Engineer Interview Questions

As the demand for skilled React developers continues to soar to 2025, companies are upping their game by posing challenging questions during interviews to identify top talent. For a senior React engineer, demonstrating a mastery of the React ecosystem, problem-solving prowess, and architectural know-how is essential.

Here are some of the toughest questions you might face when interviewing for a senior React engineer position:

1. Can you explain how React’s Virtual DOM works and its advantages?

The Virtual DOM is a core feature of React’s performance model, acting as a lightweight representation of the actual DOM. It allows React to efficiently update the UI by using a diffing algorithm to calculate the minimal set of changes needed to reflect the current state of the application in the real DOM.

When asked this question, dive deeper into the details:

• How it works: React creates an in-memory Virtual DOM tree. Upon state or prop changes, React creates a new Virtual DOM tree, compares it with the previous one…