An SSH private key isn't "something you have" - it's not a physical object, you can make copies of it.
To me it falls into "something you know". You might not be able to type it from memory into a file but in practical terms it's no different to a password, it just usually happens to reside on disk.
I use them for personal machines, and have deployed them in the past in work environments.
A few years ago I wrote a CA which can exchange oauth tokens for signed keys: https://github.com/nsheridan/cashier
Auth is handled in a browser e.g. by Google, and the CA will sign a key and return a cert with a valid token.
> I always thought it was funny that I did the same job before and after the certs.
It’s often more advantageous for the company to have people with certs (it was with MCSE and such in the 90s anyway) - more MCSE etc on staff meant it was possible for the company to attain higher partnership levels with Microsoft which often meant more lucrative contracts and so on.
So while you may have been doing the same job as before, just by having the getting the certs you added more value to the business.
SLA - correct. That’s the contract between the operator and the users which describes the penalties for not meeting agreed-upon SLO
SLO - service level objective, the stated availability (or latency or durability etc) of the service. Usually expressed as a value over a period of time (e.g 99.9% availability as measured over a moving 30 average). The SLO is measured by the SLI.
SLI - service level indicator. Simply, the direct measurement of the service (i.e metrics)
SRE - Site Reliability Engineer, usually a member of a team who is responsible for the continued availability of the service and the poor sap who gets paged when it breaches SLO or has an outage or other impactful event.
The lower-case headers is part of the http2 specification.