First Interview.. What should I expect?

It's been 9 months since I started learning web development.. Started with HTML CSS Js, then moved to react, and next.. Most of my projects are built with react js and a few in next.. I only started learning Node js like a month ago.. But with knowledge from react and next.. It hasn't been that hard. So I recently started applying for entry level frontend positions.. I somehow applied for a fullstack position and I made it to the interview.. Now the recruiter scheduled a 20 min coding challenge to test my problem solving skills.. What should I expect.. I'm a bit worried.. I have never done a coding challenge.. While I can efficiently write code and solve problems I usually get stuck and refer from stack overflow and other forums. Do they expect flawless code with no issues.? I don't know where to start.. The interview is in 4 days.