It's different depending on the company.

https://www.levels.fyi/ has a breakdown for some of the largest companies but I typically think of it as:

Eng -> Senior -> Staff -> Principal -> Distinguished

with my simple explanation being:

Eng - Able to contribute to the team

Senior - Expert on the team

Staff - Expert in your organization

Principal - Expert in your domain

Distinguished - ?? - Seems to be that you damn near created your domain. I only see these at the largest companies and a lot of times it's folks that have created popular programming languages or frameworks that the company themselves use.

Auth0 for user sign up and authorization. AWS for everything else

My little business uses PG. Had a unique need for PK IDs. It was pretty easy to make a little extension in C to generate them for us, and linking in PG was super easy (but the .so has to be on replica before loading) and we only used the TEXT type cause I didn't want to figure out making a new 128bit data-type. But can't do this in RDS.

Not sure how accurate that is, since you can buy 60TB SSDs these days.

Thinkpad t480 (t480s if you need at any cost something as slim as possible) or t580. Bonus part: nothing is soldered so you can replace any minor part without problems (yes I hate any notebook which has not easily replaceable ram or ssd or, worse, battery)

It's not super complicated, just apparently controversial.

In your $complex_app you probably have JS generating most (if not all) of the HTML seen on the page. CIJ just says that the JS should generate the styles as well so that each component in your page is self-contained.