Isn't spring boot "thread-per-request"? Some people care about that kind of performance-related stuff.

Also, I think "It gives you all errors at runtime.", should have been "It doesn't give you the errors other frameworks are able to give you at compile time." -and I kind of agree, if memory serves "Spring" is sort of synonymous with "reflection", which isn't exactly performant either.

EDIT: Wow, just read my comment and realized it comes across like I really hate Spring. I don't, I think it's nice. It's great for web apps that have human users; for services that are consumed by other services, I would probably go for something else.