We are finding Umbraco 12 to be very slow throughout. While monitoring its memory usage, when /umbraco is hit, the site will jump from < 80,000 kb of usage to upwards of 500k, and even pushing 800k. Is this abnormal? Has anyone experienced this and found a fix or should we be expecting this?

v12 is generally very fast and responsive, I run it on a Raspberry Pi 4 with no problems. There's not a lot of custom code in my site though, which is my initial suspicion. Try to run a clean v12 install and look at the performance to confirm. Memory usage seems high but it's hard to tell the real usage just from looking at your task manager. An fairy empty install for me sits at ~150.000k Other than that, I would think very large amounts of content / media could maybe make it a bit slower, but shouldn't be "very slow". I'd be curious to see what that means really. So: - have a look at an empty install, or an install with a starter kit (easily set up one with a startkit with this: https://psw.codeshare.co.uk/?TemplateName=Umbraco.Templates&TemplateVersion=12.3.3&Packages=&UserEmail=test%40test.com&ProjectName=TestWithStarterKit&CreateSolutionFile=false&SolutionName=MySolution&UseUnattendedInstall=true&DatabaseType=LocalDb&UserPassword=test123456&UserFriendlyName=Test&IncludeStarterKit=false&StarterKitPackage=Umbraco.BlockGrid.Example.Website&OnelinerOutput=true) - evaluate what custom code/packages you have installed, maybe something is leaking or grabbing a lot of memory / CPU, making it slow