I applied online.

• Hackerearth: 5 JavaScript objective questions, which were simple ones like (function(x) { return (function(y) { console.log(x**2); })(2) })(1).
• UI Basics round: HTML5, CSS3, JS, React, and Redux.
• UI Advance round: JS, React, and Redux, with questions like Redux life cycle, React life cycle, parent-to-child and child-to-parent communication in React, import and require, and file upload implementation in React.
• Hiring manager round: VP of Engineering, a technical guy who asked about PWA, AMP, event loop, and CORS.

All the rounds were smooth except the third one. That round was handled by a so-called Rockstar who was a bit arrogant, senseless, and baseless. He thinks that he knows everything. He wanted to finish the interview fast, so he asked random questions, and if you tried to answer, he wouldn't listen to you and would move to something else. He was not loud or clear, and he showed attitude on his face. The company boasts heavily that they are Facebook-funded.

File upload implementation?