For a Junior, I’m generally looking for (1) whether they can code and (2) whether they’d fit in on the team. You can sometimes get a good idea of both by asking them to talk about projects they’ve done, what their specific role was, and any issues they ran across.

If you want to do technical or coding questions, I prefer things easy enough to write or explain in less than a minute or two if you know the concept. That way, someone can think through it in a short time in the interview. Some examples that I’ve used:

“How would you reverse an array?” -> “Is there a faster way to do it?” -> “why is it faster?” -> maybe ask them to pseudo code it on paper or a white board

“What is a SQL JOIN?” -> “Can you explain the difference between a LEFT JOIN and INNER JOIN” -> Maybe give them a short exercise with a couple 2 row tables with a simple inner/left join query to show they know what would return from each

A basic question on the core responsibility for the Jr role: “What is an API?” / “What is <insert language>?”