I found it crazy useful to study old, established, mature technologies, like relational databases, storage, low-level networking stack, optimizing compilers, etc. Much more valuable than learning the fad of the year. For example, consider studying internals of Postgresql if you’re using it.

Learn to talk to people and maintain connections. It is most invaluable skillet that will help you both carreer wise and professionally. The more people you know the better it is for your carreer. Learn to present yourself. Visibility matters very much, so it also good to “sell yourself” sometimes. There is really fine balance between making a sell and just bragging, people don’t like second, but okay with first. Learn to teach other people and help them. Most troubleshooting experience I get now is from helping other people. They have a completely different way of doing code that I am (as a whole) and I am just getting this free xp by helping them and also adding one more trouble to my personal solution cupboard.

As for technology, pick what you like and master it, but also make a peeks at what is currently “in vogue”. For example I really have no depth knowledge in the current frontend space, but I did take a passing looks (and build simple tutorial projects) with react, angular and dart. It didn’t really required a much effort from me, but this helped in the long run to be aware.

There’s three approaches I use here.

1. Find some bit that you bonk your head into regularly. Maybe it’s query optimization. Maybe encryption or auth. Maybe infra setup. You can usually muddle through it by reading the 5th comment on SE or finding a coworker’s working code. But you don’t actually understand how or why it works.

2. Think more broadly of where you want your career to be in 5 years, or what you want your next job to be. Map out what you know and what you need to know to be successful in that role. Study the gaps. Sometimes it’s not technical skills.

3. Pick a project you find interesting that has nothing to do with your current job responsibility. Frontend? IoT? Systems level stuff? Dig in! You will find that unrelated computer stuff is in fact all related in some way.

The least adventurous approach is to work at the edges of what you’re already doing. Are your apis usually consumed by react components but you’ve never written one? Try writing a react app that consumes one of your services and see where the pain happens. Even if you never use react again you’ll have learned something about your work from a new perspective.

Don’t spend too much time on anything that isn’t fun. Chase joy and fail fast.

As someone with more than 5LOE I’ve found that technology matters less and general concepts are more valuable.

So look at system design concepts, how infra you use typically works (pubsub, databases, etc), how companies solve problems (engineering blogs from companies like slack, meta etc)

Learning new languages only helps if you are currently working on something obscure.

I mean I’m being honest I’m a little bit in love with Rust haha, so I can recommend learning that if you haven’t yet, it has teached me the most of how to design nice programs/libs (in an efficient manner) and generally just feels nice to write. And a very relevant side-effect: it seems like it has a rapid growth also on the job-market. I really feel that growth in terms of improving library quality and tooling (rust-analyzer is I think really the best language server by now), not the least seeing ever more often something like this: https://opensource.googleblog.com/2023/06/rust-fact-vs-fiction-5-insights-from-googles-rust-journey-2022.html)