[etjossem]

I've typically seen teams that look like this: Designer, Front-End (or "UI", or JS) Developer, and Back-End (or Python, or Ruby, etc.) Developer.

Designer is responsible for all UX tasks that don't involve writing lots of code, Front-Ender writes all client-side code "above the API." API code, devops, and DB admin falls to the server-side engineer. You might create a separate mobile role too, if you're working on a mobile client. If one of these roles gets contracted out, it's usually the designer or the mobile dev.

Then again, I'm most familiar with small teams. You see more specialization at larger firms.

[drinchev]

Yes. I always thought it is like this.

As a front-end developer :

I've been doing JSPs, but I've rarely modified .java files.

I've been doing JS, but I would not be confident in pushing commits to the server-side code of a NodeJS project.

I've been doing REST API calls, but it would be hard for me to change database queries.

etc.

That's what I think I'm best at. ( You know as every developer it's not a big deal to dig into any problem, but professionals usually rely on experience ).