Ask HN: What back end skills do I need to become 'fullstack'?

Hi HN, I'm a 'frontend' web developer. I've been working with web apps for the last 3 years and I'm fairly proficient with my stack. I have a good understanding of how the backend works in a general sense too. I've worked as a freelancer and am currently working with a team building a product with react.

I want to become a fullstack developer, at least enough to be valued in a backend role as well. I'm trying to come up with a list of concept/skill checkpoints based on what I would need to typically do as a 'backend' developer.

Here's what I've put together so far, in no particular order:

> Data modelling and using a database: simple e-commerce site on Postgres

> Building an authentication system: implementing a server-side google oauth2 login

> Building & deploying an API service of 3 different types: db interaction, using auth, using 3rd party APIs (nodejs/python)

> Serving static files (nginx)

> Deploying and putting a simple CMS site together (wordpress)

> Deploying a full app with a domain name

> Building and deploying a batch job to create reports from the database

> Migrating app + data from one VM to another

What do you all think? Something I should add/remove? Should I take a completely different approach?