There are a few to scale, like Emilia Romana (Italy, 8000 employees) or Mondragon in Spain (79K employees), unfortunately not in tech. I only know of DATEV with some 8000 employees in that sector.

The co-op model in general is so very promising and those that still exist are really successful and from video documentations I watched, the employees seem to be content, if not getting rich. The problem is that this model runs counter to the very core of capitalism and as such faces a lot of criticism.