Ask HN: Looking for recommendations to spend my remaining training budget

I have about 1k€ left of my training budget for this year, which does not carry over to the next year in case it's not used.

I'm looking for a course, books, or maybe a certification (although I'm not really a fan of this industry).

Some topics I'm interested in are:

- Application security, as in actually focusing on security at the software level. I already work in security (offensive, cloud/infra, security in CI / CD...), but I lack knowledge when talking at the software/algorithm level. For example, identify security vulnerabilities in code (beyond common ones), discuss whether one algorithm is better than other for a particular use-case, etc.

- AI in general, although more particularly into the operations side (this so-called "MLOps"). I know Andrew Ng has an updated course in Coursera covering this topic, but it's free, so I don't need to use this budget.

- Leadership. So far, I have used this year's budget in improving my leadership skills, especially communication skills. I have led a few teams over my career, and so far so good. Everyone loved my way of leading, except for one guy. However, this is an area of constant learning, so any course or must-read book is welcome.

So, in summary, do you have any recommendation for courses or books covering any of those topics that you think are worth?

I'm more interested in courses / video material, as with 1k I could buy dozens of books that I probably I won't have time to read.