Uber 5b interview

I have Uber interview scheduled for level 5b.
One of the coding rounds is depth in chosen tech and it entails:

This interview assesses depth in your chosen area of specialization/technical depth via writing code that solves a problem that would be similar to what you would do in the job.
Specializations include: Backend, Frontend, Android, iOS, Data, Machine Learning/AI, Security, SRE

My expertise is with backend technologies. I totally understand having a different system design interview for that but I was wondering what type of coding questions can I expect for backend tech. A few examples will be very helpful.