See pics.
(https://i.ibb.co/gS5Thn0/2023-09-22-1.png) (https://ibb.co/486T3Qb)
(https://i.ibb.co/0Q2G3bj/2023-09-22.png) (https://ibb.co/8Xs7VZD)
Looks like a low powered machine, RAM is also maxed out, as for the CPU depending on the traffic I'm not surprised about the CPU being maxed out
Intel(R) Core(TM) i5-4690 CPU @ 3.50GHz (4 cores). On Proxmox.
I gave it 4 GB RAM, previously it had 8 GB or 10 GB. Still used a huge percentage of its RAM (sometimes).
As you see, it is sorted by memory usage percentage. Those 16 GB compressed RAM are in yellow (caches?). Also, to compress 16 GB within a total of 4 GB means it is very, very compressible data (ASCII plain text, HTML or something like that).
I think it only happens when accessing the firewall through dash.zenarmor.com, since usually the CPU is at very low usage (about 1% or so) and total RAM usage is between 480 MB and 550 MB.
Now I have switched to Minisforum UN100C (less than 200 Euro/PC, only two Ethernet ports and one WiFi, has one Intel N100 processor with 4 cores, 16 GB RAM and 512 GB SSD). I am no longer using Proxmox for Opnsense. Works okay (Gigabit Zenarmor) despite having Realtek Ethernet, instead of Intel.