CO2 is an old refrigerant that has returned because of its tiny climate impact. It is non-flammable and cheap, and its GWP is 1 by definition. The challenge is pressure: CO2 systems run at several times the pressure of HFC systems, so compressors, pipes, valves and safety devices must be designed specifically for it.
CO2 has a low critical temperature of about 31 °C. Above that, it cannot condense in the usual way, so the system runs in a transcritical mode with a gas cooler instead of a condenser. In hot climates like most of India, this lowers efficiency unless the system uses extra technology such as ejectors or parallel compression. That is why CO2 is used mainly in larger supermarket and cold-storage systems, and in some plug-in beverage coolers designed for it.
For a typical restaurant or shop, R744 is less likely to appear in a single plug-in cabinet than R290. Where it is used, servicing needs technicians trained in high-pressure work and specific tools.