Use expressjs with mongodb or mysql for this. You need design database tables yourself based on the question.
a) We have two entities 'candidate' and 'test_score' b) candidate has properties name, email address c) Every candidate has to give 3 tests like 'first_round', 'second_round', 'third_round' and scoring for every test is done out of 10.
Now using expressjs, only need to create api to do the following
a) Insert a candidate into database b) Assign score for a candidate based on the test c) Get highest scoring candidate and avg scores per round for all candidates