How to pick a project from multiple options?

A couple thoughts:

1. If the goal is to push the boundaries of your technical skills, then don't pick projects/tasks that you already know the answer to (aka know how to solve).
2. One thought exercise that could help is rank the projects according to your best guess around "pushing your boundaries", and provide some rationale for each, then ask a coworker/teammate (preferably someone who is more senior than you) to review and provide feedback.
3. Even "boring" projects have the opportunity to push the boundaries of your technical sills – since there is probably opportunities to revisit the "basics" and dive deeper to make sure you thoroughly understand them.

Similar to the advice we shared in the masterclass about joining a new team or company, I believe one criteria (perhaps the most important criteria) should be: the people you'll work with on the project.

I know you mention technical skills as the priority, but the people you work with will dictate how much you learn the skills.

The people will also be the best predictor of how much technical depth the project has. I recommend you look at the work of the potential people on the project and evaluate if you have something to learn. Look at:

• Their code commits
• What docs they've authored
• What meetings they take part in

Assuming these aren't solo projects, the biggest factor is definitely the people. If they're folks you respect and can learn from, the project has a much higher chance to be beneficial to you and a good experience to go through. Conversely, it's not worth working on a meaty project of good scope if the stakeholders on it are miserable to work with.

When it comes to judging technical depth (super important going from senior -> staff), I recommend following the advice here: "How do you choose an opportunity for technical depth?"

This is an incredible thread as well: "How to figure out what the most important projects are?"