From the PlanetScale perspective keep in mind the ability to shard. What happens when the largest single node Aurora instance can no longer keep up with application/traffic demands?
I ask because we see it more often than not, and for that situation sharding the workflow is the best answer. Why have one MySQL instance responding to request when you could have 2,4,8...128, etc MySQL instances responding as a single database instance? They also have the ability to vertically scale each of the shards in that database as it's needed.
Even MySQL benefits from these changes as well. What we're really discussing is random primary key inserts (UUIDv4) vs incrementing primary key inserts (UUIDv6 or v7).
PlanetScale wrote up a really good article on why incrementing primary keys are better for performance when compared to randomly inserted primary keys; when it comes to b-tree performance. https://planetscale.com/blog/btrees-and-database-indexes
The Phenom II will always have a special place in my heart being the CPU of choice in my first CPU build in 2011. It's wild to see it's still being compared to modern CPUs, and winning the against the competition in select benchmarks.
I completely skipped the FX disaster / Intel dominance phase by holding on to a Phenom II X6. At the time, my upgrade policy was "when twice the performance is available for the same price as the old part". That never quite happened with Intel's 4 core parts.
One of my old builds was a Phenom II X2 550 Black, where I found that I could either overclock it, or unlock two more cores, but not both. I chose the cores, and it ran that way for a long time. That was one of the best bang-for-the-buck deals I ever ran into for a CPU.
Coming from a Linux Admin background, I would suggest installing a Wordpress website to learn more about the LAMP stack and seeing how all the pieces fit together. Once you get it working on a box, look at how you could scale out the Apache and Application layer.
From there one of my first developer projects was creating a Flask Application which uses Python. I think understanding the mechanics of Wordpress, helped me design and build the Flask Application. (Which could be a blog or whatever you want to put online.)
I ask because we see it more often than not, and for that situation sharding the workflow is the best answer. Why have one MySQL instance responding to request when you could have 2,4,8...128, etc MySQL instances responding as a single database instance? They also have the ability to vertically scale each of the shards in that database as it's needed.