Hello,

The eligibility criteria of UPSC states that candidates need to attain 21 years age and are required to pursue graduation in any discipline from a recognized university, those in final year are also eligible. now the engineering discipline which overlaps with optional syllabus are civil, mechanical and electrical, apart from this the large portion of UPSC constitutes non-engineering or non-technical subjects such as you have to study polity, history, geography, ethics, economics etc, but as I said there are no barriers as such because candidates belonging to diverse backgrounds such as medical, commerce, engineering(other than the mentioned disciplines) too qualify the exam, these candidates are enough proof that diverse discipline graduates do qualify, yes but the advantage of having graduation subject as optional is that the optional syllabus is huge nothing short of graduation level study so if you're already well acquainted with it, then it helps to a large extent in the preparation process.