How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a medium difficulty System Design question, commonly asked during Onsite rounds at Citi.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Citi during technical interviews.

Explain OS and networking basics

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's understanding of operating system and networking fundamentals, covering processes, threads and context switching, concurrency versus parallelism, TCP/UDP and flow versus congestion control, and the end-to-end web request and browser rendering pipeline.

Citi

Sep 6, 2025, 12:00 AM

Software Engineer

Onsite

System Design

Systems Fundamentals Quickfire (Onsite Software Engineer)

Answer concisely but precisely. Use diagrams or bullets if it helps.

Processes, Threads, and Context Switching

What is the difference between a process and a thread?
What costs are involved in a context switch?

Concurrency vs. Parallelism

Contrast concurrency and parallelism.
Describe one common concurrency bug and a mitigation strategy.

TCP vs. UDP; Flow Control vs. Congestion Control

Compare TCP and UDP and give typical scenarios for each.
Briefly explain TCP flow control and congestion control.

From URL to Page Render

From entering a URL to the page rendering, outline the major steps, including: DNS resolution; TCP/TLS handshake; HTTP request/response; and the browser’s rendering pipeline.

Assume a modern browser and OS; note any meaningful variants (e.g., HTTP/2 vs. HTTP/3) where relevant.

Solution

Show

Submit Your Answer

Loading comments...

Browse More Questions

More System Design•More Citi•More Software Engineer•Citi Software Engineer•Citi System Design•Software Engineer System Design