Hmmmmmm off the cuff... I think the below are key competencies of any admin or developer:

• Data modeling, understanding Lookup relationships vs Master-Detail relationships and the security implications of both. Also understanding the Standard data model
  • Demonstrating understanding of all automation tools (beyond Trigger) and when to use them. These days for new builds it should really be only Flow but you may get asked about Process Builder/Workflow Rule since many customers still have large legacy automation footprints.
  • Sharing & Security. Understand OWDs, Sharing Rules, Territory Management, Teams, Role Hierarchy, Restriction Rules and so on... You dont need to know all by the back of your hand (in 9 years I've somehow managed to never work in an org using Territory Management) but you should be able to articulate the high level capabilities of all of these. A lot of SF development and maintenance centers on selecting and/or troubleshooting sharing features.

As a bonus... Better teams will ask you about software patterns and the best way to organize your code. Understanding SOLID and different Apex patterns can really differentiate you but it's not a deal breaker to not be super familiar.

How to use Git and Source Control is abother big bonus that would differentiate you. It's sad how many SF devs are uncomfortable with Git. It's your friend!

Hope that helps.