Have a look at the About Us section in the interview preparation for our full stack engineers, to make sure this company seems like a good fit for you
We will be discussing your experience as a contributor to front-end code, and as a lead, we will expect you to have opinions on better or worse ways to keep large amounts of front end code easy to maintain. You don't have to convince us your opinions are correct, but you should be able to articulate your rationale for your opinions, how strongly you hold those opinions, and what it would take for you to change your mind.
Think about how you deal with testing, routing, property drilling, asynchronous calls, callbacks, css organization, code organization, and code reuse. You should be able to give plausible answers for how you would keep all of these aspects of the code maintainable even as the feature set increases in both number and complexity.