Disclaimer: I went through the interview process almost 10 years ago. I think I'd initially applied for the Gen SWE position, the interview process was changed to Frontend SWE after talking to a recruiter (at the time, they really needed Frontend SWEs), but my offer letter & job title were actually Gen SWE. I did frontend duties for my first 2 years and last year, and then more of the algorithmic & research stuff that Gen SWEs do for the middle 2 years.

"Frontend" at Google is everything from the client (usually Javascript, mobile platforms have their own job titles) back through the webserver and RPC interface to the rest of Google's services. This is somewhat distinct from how the rest of the industry does it; "Frontend SWE" at Google is almost equivalent to "Full Stack Developer" at many startups, because the full server-side code for many startups is like the webserver code for many Google services. It's also why Frontend SWEs need to know at least one server-side language (Java or C++).

The interview process reflects this. When I interviewed, and when I conducted interviews, Frontend SWE candidates usually had 2 interviews that focused specifically on frontend technologies (usually things like Javascript, DOM traversal, web platform APIs, sometimes knowledge of how HTTP works or what your browser is doing when you make a request) and 2 interviews on Gen SWE topics (algorithms, data structures, system design, general programming knowledge).

The Gen SWE position focuses much more on algorithms - Gen SWEs at Google are usually the folks implementing the backend services that the webservers call out to, along with various data pipelines etc. Typically your task is "Design and implement an algorithm to do X, and make sure it runs efficiently", and the interviews reflect this.

When I was there the differences in salary were fairly negligible. I think that Frontend SWEs may have come in with a slightly higher salary & stock grant (though this was an artifact of the times; in 2008 very few devs really knew Javascript well, in 2018 virtually everyone does), but they share the same engineering ladder, so it equalizes over time and your individual job performance matters much more.

Thank you so much for responding! This is very helpful.