> I'm not sure how you can spend 5 years and not learn at least one thing in depth. You'd have to rotate technologies every 6-12 months and there's not that many technologies.

That's kinda how SV is these days though. It's very common for engineers to jump companies every 1-2 years for a long period of time and the companies very frequently undergo a shift in technologies while engineers are there. So, unless you join FAANG or some super stable company - I could see it being natural from just how the market works that you end up having a very short fat engineering career.

For myself, the only consistent thing from my five jobs over the last 7-8 years is that they've all had JavaScript (actually - one had CoffeeScript but then we migrated to JavaScript when I was leaving) - but that's mostly just because of the nature of web development. In the middle of my sixth job search right now and it's looking to be a backend role that won't be in JS now. So, there goes that stability...

Personally: fullstack LAMP -> fullstack Python + Django -> frontend role with backbone/knockout/angular and majority of vanilla JS and CSS -> fullstack Python + Django + CoffeeScript -> Fullstack Angular + Node -> Backend Node with shift to TypeScript near the end

You wouldn't say you have deep knowledge of JS & front end frameworks?

Nope. My frontend knowledge has disappeared in the last year as I've done almost all backend. My knowledge of JS is enough to get the job done but deep knowledge? How could it be - I'm constantly building products, not toying with the minute of performance optimization or creating some impressively large framework. The stuff I do is extremely lean and relies very little on language nuances. The stuff I do could be done easily in many languages - it just happened to be in JS a lot of the time.

What do you classify as deep? I feel comfortable with JS and have a vague understanding of the internals of front end frameworks, but I wouldn't consider myself to have deep knowledge of either.

It's relative to your other skills. If you were a novice at everything and intermediate at JS then that's the trunk of your T.

On the spectrum from compilers to machine learning to frontend, there are plenty of technologies.

I could imagine it happening, if you've worked as a contractor on 12-18 month gigs per company for the last 5 years, testing things out and getting a feel for what areas you like to work in the most.