A new project utilises the current Raspberry Pi 4 into a powerful mini-server. The project can run off an M.2 SSD and should be fairly simple to build.
https://www.notebookcheck.net/Raspberry-Pi-Transform-the-popular-single-board-computer-into-a-server-with-the-NODE-Mini-Server-V3.489603.0.html
I think the node server v3 supports an mSATA drive instead of an M.2 drive. M.2 drives are too long for the raspberry pi form factor.