There were 4 rounds of interviews:

1. 15 min HR interview
2. 3-hour test task (I've done it in 6 hours, not sure why, but they proceeded to the next round)
3. 1-hour tech interview
4. 30 min CTO interview

I received timely feedback from HR. Everything was good, and I accepted the offer.

Node.js Event Loop

Latency issue between client and server (describe possible ways where the problem lies)

CORS