A Raspberry Pi 3 Model B
It’s connected to my 3d printer and runs octoprint allowing me to upload print jobs. and control the printer from my home network.
It serves up the Pi camera video stream.
It can also switch the printers light on and off.
No cluster setup.
I had one of these, it worked perfectly for years. I might even still have it. I remember it being a significant leap in size and cost per MB.