I want to build an online judge (competitive programming platform) similar to codechef or codeforces as a project

I am looking forward to creating my own personalized online judge but I have no idea from where should I start. What technologies I need to build this.

I especially need to know how can we implement code submission and code output checking functionality

I am a college student and pretty familiar with node.js, express.js, and MongoDB. So I can create frontend and basic functionality such as authentication etc...