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Lakshay Jawa

Lakshay Jawa

Engineering Leader | Architecting AI-Driven Execution | Scaling Distributed Systems

System Design · Behavioral Interviews · Posts

About nSkillHub
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A passion-driven space for learning — system design, Java, Spring, and software engineering best practices. As a software engineer with years of experience, this blog shares insights, deep-dives, and interview prep material. Future topics will expand into movies, photography, travel, and more. Stay tuned!

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Recent

Give Me an Example of a Time You Identified a Problem No One Else Saw and Took Ownership of Fixing It

·22 mins
Behavioral Interview Behavioral Leadership Star-Method Em Director
S1 — What the Interviewer Is Really Probing # The exact scoring dimension is proactive vigilance and unassigned ownership — the disposition to notice a signal others missed, run it to ground without being asked, and decide that fixing it is your job before anyone tells you it is. This is not a question about being a good citizen. It is a question about whether you create a different environmental outcome than someone with identical authority and identical information would create by default.

WhatsApp / Chat Messaging System

·33 mins
System Design Classic System-Design Classic
1. Hook # WhatsApp delivers 100 billion messages every day to 2 billion users across 180+ countries — all end-to-end encrypted (E2EE), with sub-second latency, and with a global engineering team historically smaller than 50 engineers. The system does this while providing strong delivery guarantees (a message is either delivered exactly once or the sender knows it was not), preserving per-conversation message ordering even when users switch networks mid-send, and maintaining ephemeral server storage so that once a message is delivered it lives only on client devices.

Instagram

·30 mins
System Design Classic System-Design Classic
1. Hook # Instagram processes 100 million photo and video uploads every day, serves 4.2 billion likes, and delivers personalised feeds to 500 million daily users — all while keeping image loads under 200ms anywhere in the world. The engineering challenge is three-layered: a media processing pipeline that converts every raw upload into five optimised variants before the first follower ever sees it; a hybrid fan-out feed that handles both 400-follower personal accounts and 300-million-follower celebrities without write amplification blowing up; and an Explore page that must surface genuinely relevant content from a corpus of 50 billion posts to users who have never explicitly stated what they want. Each layer has a distinct bottleneck, and solving one often creates pressure on the others.

Tell Me About a Time You Disagreed With Your Manager's Direction but Still Had to Lead Your Team to Execute It

·22 mins
Behavioral Interview Behavioral Leadership Star-Method Em Director
S1 — What the Interviewer Is Really Probing # The exact scoring dimension is disagree-and-commit discipline — the ability to hold your professional obligation cleanly separate from your personal conviction. This is one of the most important leadership tests in any panel because it exposes whether your integrity survives disagreement. Almost every candidate says they disagreed and still executed. Very few demonstrate that they executed without hedging, without signalling their displeasure to their team, and without protecting themselves by leaving a paper trail of “I told you so.”

Describe a Situation Where You Had to Make a High-Stakes Decision With Incomplete Information

·18 mins
Behavioral Interview Behavioral Leadership Star-Method Em Director
S1 — What the Interviewer Is Really Probing # The exact scoring dimension is judgment under uncertainty — the interviewer is not testing whether you made the right call. They are testing whether you have a structured mental process for making consequential decisions when the information needed for certainty either doesn’t exist yet or can’t be obtained in time. This is the difference between a leader and an analyst: analysts wait for completeness; leaders learn to act on enough.

Twitter / Social Media Feed

·25 mins
System Design Classic System-Design Classic
1. Hook # Twitter at peak serves 600K tweet reads per second while simultaneously processing tens of thousands of new tweets. The naive approach — querying who you follow, then fetching all their tweets, then sorting — collapses instantly at scale. The real architecture is a masterclass in the write-amplification vs read-latency trade-off, and the edge cases (Lady Gaga following Justin Bieber, or vice versa) reveal why no single strategy wins.

Led a Team Through a Significant Technical Change They Were Resistant To

·19 mins
Behavioral Interview Behavioral Leadership Star-Method Em Director
S1 — What the Interviewer Is Really Probing # The scoring dimension here is change leadership under resistance — not change management in the HR-training sense, but your ability to drive conviction-led transformation while preserving the trust of the people who are pushing back. Interviewers care about whether you understand why resistance exists. Is it fear of irrelevance? A legitimate technical objection? Loss of ownership over something engineers spent years building? Leaders who conflate all resistance as “people being difficult” and steamroll it create short-term compliance and long-term resentment. Leaders who can diagnose and address root cause create lasting followership.

URL Shortener (bit.ly)

·14 mins
System Design Classic Url-Shortener Base62 Distributed-Systems Caching Scalability
1. Hook # Every time you click a bit.ly or t.co link, a distributed system silently resolves a 7-character code to a full URL and redirects you — in under 10 milliseconds — before your browser even renders the loading spinner. Behind that invisible handshake sits a deceptively rich design problem: how do you build a service that creates billions of short codes, never loses a mapping, and serves hundreds of thousands of reads per second with single-digit millisecond latency, all while preventing abuse, surviving data-centre failures, and staying profitable?