Some people have a very limited space behind the counter so to make the most of this space what we do is supply them with an ultra-small minicomputer. Our current model is hardly larger than a deck of playing cards (133.8 x 43.1 x 94.2 mm). It is quite powerful with a CPU Intel Atom Processor, Dual Core, 1.33 Ghz and 8 GB. They can be installed as well in walls, cabinets or ceilings. This is required in shops sometimes as some video surveillance cameras require the computer to be right up close to them.
What I particularly like about them is that they are fan-less so they make no nose and they can be put in a sealed area.
In practice, we find them reliable, and they come with a three-year warranty.
As the price drops I expect that they will soon replace the desktop pc’s.