Hi! I'm Aryansh Kurmi

An 18-line Java skeleton with one TODO: poll every server every interval and store its stats. It looks like a loop and a sleep. It is actually a question about drift, head-of-line blocking, failure isolation and unbounded hangs — and on Java 21, about whether you still need a thread pool at all. The full design, then how it scales to a million targets.

A DSA round I sat where the question looked like a nested-array chore and turned out to be a difference array in disguise. Every section starts with the kid-level version, then drops into the real Java — brute force, the delta trick, a full dry run, and why the answer I actually gave in the room was subtly wrong.

A Codeforces Div. 2 D that looks brutal — replace a[i] with a[i-1] - a[i] + a[i+1] whenever its two neighbours share parity — turns out to be nothing but sorting. Here is the whole thought process: how the difference array collapses that formula into a single adjacent swap, why the parity gate becomes 'same parity', and why sorting each run ascending is provably optimal.