1. Networks, Caching, Building a nodejs server from scratch

I had two technical rounds of one hour each. In the first round, I was asked about my projects, why I choose nodejs, the difference between Postgresql and mongodb, how can we share our data with a third party without affecting the sensitive data.. etc. I also had a dsa problem, we are given a sorted array and an element x and have to find if there exist any pair i , j such that i < j and arr[i] + arr[j] == x. After solving this,he changed the question to find four index i,j,k,l such that i < j < k <l and arr[i] + arr[j] + arr[k] + arr[l] == x. In the second round, Again we had a brief discussion about my projects then I was asked about package manager , modules , package.json , package.lock.json , how modules stored in node_modules folder , npm install vs npm install some_modules ,.... etc. we had a dsa problem, we are given n modules and m relation between them like [x,y] x only install after installing y, we have to print a valid order of installation. what happens when we search for some URL in our browser.