Leetcode, system design books, and mock interview
Interviews are designed to evaluate three key dimensions of a candidate – Ability, Knowledge and Intent.
Ability
Demonstrated ability to successfully ramp up and accomplish a project with a certain technical and organizational scope. The context of the work need not match the role being hired for.
Knowledge
Prior experience in a similar scale, technology, language, framework and organizational structure.
Intent
The aspirations of the engineer on their career goals, learning goals and items categorized as culture fit.
Companies do not know how to evaluate properly for ability and intent. They make it up by interviewing for knowledge.