Hi,

All the best for your UPSC exam in 2022, if you plan to keep MBA as your back up plan you will need working experience and it totally depend on the country and the university that you're applying to. For say, If you apply for MBA in USA you will need a minimum 5 year of working experience and that too if you manage to clear GMAT exam. But since you're from a STEM background it will definitely help you to have a successful career abroad.

All the best!