Ask HN: Best conferences to attend?

Hi HN! What are the best conferences to attend for engineers (software/hardware)? I know that using the word 'best' may be a bit ambiguous since everyone has their own professional goals, and what is best for one individual may not be the best for another.

Feel free to list the conferences and give a bit of background as to what to expect when attending?

If it helps, I'm about ~3 years into my career, and looking to continuously keep learning, improving, and growing my network. I see conferences advertised here and there, but not sure which ones are worth attending. Any additional tips and advice would be greatly appreciated!