Mastering Node.js Event Loop Fundamentals

💭 During my LeetCode grind, I ran into a real problem… You keep solving problems daily… but after a few days, you can’t even remember what you solved. No proper way to revise, no clean tracking, nothing structured. So I started looking for tools that could help me track my submissions… but honestly, I found nothing that actually solved this properly. Then I went hunting for APIs 👀 I came across a few options — but they had issues: • Strict rate limits • Not reliable enough for real projects • Not scalable if a user has a lot of submissions None of them felt “production-ready”. Finally, I dug deeper and reached the LeetCode GraphQL API… It was powerful — but not straightforward. Still, I decided to build on top of it and make it usable. And that’s how this came to life 👇 ✨ LeetTrack — a simple LeetCode progress tracker 🔗 https://lnkd.in/dPJYR32Z 🚀 What it does: • 📅 Revision Mode → revisit problems from any date range • 📊 Clean dashboard to actually see your progress • 📌 Easy / Medium / Hard breakdown • 🧾 Recent submissions, properly structured ⚡ Zero friction: • No login required • Just enter your username and start instantly ⚙️ How it works: • Fetches your latest 20 submissions initially (API limitation) • Then keeps auto-syncing in the background • Builds your own personal dataset over time 🛠️ Built using: • Backend: Pure Java + MongoDB • Frontend: Next.js + Tailwind CSS • Deployment: Render + Vercel 📌 Code : Frontend Repo: https://lnkd.in/dJCejDSw Backend Repo: https://lnkd.in/daiNFrf3 Built this to solve a real problem I personally faced — simple, useful, and no unnecessary complexity. If you’re grinding LeetCode, this might actually help you stay consistent 👇 Would love your feedback 🙌 #LeetCode #FullStack #Java #NextJS #WebDevelopment #CodingJourney #Projects

🚀 Skill Boosters — Notes #6: Struggling to understand how Node.js handles multiple requests? Let’s simplify it 👇 Link: https://lnkd.in/ebN-Cdmy In Node.js, everything revolves around a few powerful concepts: 👉 Event Loop 👉 Single Thread 👉 Asynchronous Programming 👉 Event-Driven Architecture 💡 Here’s the magic: Node.js is single-threaded, yet it can handle thousands of users at the same time. How? Because it doesn’t wait. 🔄 Event Loop Think of it as a manager that keeps checking: “Is the main thread free?” “Yes? Let’s execute the next task.” ⚡ Async > Sync Instead of blocking: ✔ Sends heavy tasks (API, DB, file) to background ✔ Continues handling other requests ✔ Comes back when task is done 🧵 Single Thread ≠ Slow Node.js uses: 👉 Single thread for execution 👉 + Background threads (libuv) for heavy work 🎧 Event-Driven System Everything is based on events: Request comes → event triggered Task completes → callback executed 🔥 Real Power This combination makes Node.js: ✔ Fast ✔ Scalable ✔ Perfect for APIs & real-time apps 💭 One Line Takeaway: 👉 Node.js= Single Thread + Event Loop + Async = High Performance Backend If you're building backend systems, mastering this is a game changer. 💬 What confused you the most about Node.js earlier? Event loop or async? #NodeJS #BackendDevelopment #JavaScript #WebDevelopment #SystemDesign #Programming

𝗜 𝘀𝗽𝗲𝗻𝘁 𝟯 𝗵𝗼𝘂𝗿𝘀 𝗱𝗲𝗯𝘂𝗴𝗴𝗶𝗻𝗴 𝗔𝗻𝗴𝘂𝗹𝗮𝗿. 𝗧𝗵𝗲 𝗽𝗿𝗼𝗯𝗹𝗲𝗺 𝘄𝗮𝘀 𝗮 𝘀𝗶𝗻𝗴𝗹𝗲 𝘄𝗼𝗿𝗱: 𝗮𝗻𝘆. 🤦♂️ TypeScript evangelist on my team. Told juniors to "always type everything." Then I did this: // ❌ "Just for now" — famous last words getUserData(): any {  return this.http.get('/api/user'); } - "Just for now" became 4 months of 𝗮𝗻𝘆 quietly spreading through the codebase like a virus. - No errors. No warnings. Just TypeScript politely stepping aside while I shot myself in the foot. - The bug? A backend team renamed 𝘂𝘀𝗲𝗿.𝗳𝘂𝗹𝗹𝗡𝗮𝗺𝗲 to 𝘂𝘀𝗲𝗿.𝗳𝘂𝗹𝗹_𝗻𝗮𝗺𝗲. TypeScript should've screamed. Instead, it shrugged — because any told it to stay out. - We found it in production. Via a client email. // ✅ What "just for now" should actually look like interface User {  id: number;  full_name: string;  email: string; } getUser(): Observable<User> {  return this.http.get<User>('/api/user'); } -Now if the backend changes that field — TypeScript breaks the build before it breaks the client. 𝗧𝗵𝗲 𝗿𝗲𝗮𝗹 𝗹𝗲𝘀𝘀𝗼𝗻: 𝗮𝗻𝘆 isn't a type. It's a debt you take on with zero interest rate — until suddenly it compounds all at once. The worst bugs aren't the ones TypeScript catches. They're the ones you told TypeScript to ignore. 💬 𝗛𝗼𝘄 𝗺𝗮𝗻𝘆 𝗮𝗻𝘆 𝘁𝘆𝗽𝗲𝘀 𝗮𝗿𝗲 𝗵𝗶𝗱𝗶𝗻𝗴 𝗶𝗻 𝘆𝗼𝘂𝗿 𝗰𝗼𝗱𝗲𝗯𝗮𝘀𝗲 𝗿𝗶𝗴𝗵𝘁 𝗻𝗼𝘄? 𝗕𝗲 𝗵𝗼𝗻𝗲𝘀𝘁. 𝗡𝗼𝗯𝗼𝗱𝘆'𝘀 𝗷𝘂𝗱𝗴𝗶𝗻𝗴. #TypeScript #Angular #Frontend #WebDevelopment #CleanCode #SoftwareEngineering

🚀 Productive Day of Learning & Building! Today was a solid mix of backend fundamentals, DSA, and personal development: 🔹 Built a backend server using Node.js HTTP module (without Express) → Explored core response methods like res.writeHead() and res.end() → Understood how higher-level methods like res.status() and res.json() (in Express) are abstractions built on top of these 🔹 Revised Node.js Event Loop phases → Deepened understanding of the difference between I/O Callbacks phase and the Poll phase → Learned how the Poll phase handles incoming I/O events, while I/O callbacks execute deferred callbacks from previous cycles 🔹 Solved a Stack-based problem on LeetCode → Next Greater Element (focused on optimizing using stack) 🔹 Prepared a strong self-introduction → Highlighted projects, key learnings, and challenges faced 🔹 Continued reading The Psychology of Money → Building better communication and financial perspective Consistency over intensity 💪 Every day is a step closer to becoming a better developer. #NodeJS #BackendDevelopment #DSA #LearningInPublic #SoftwareEngineering #Consistency #LeetCode

Deep Diving into Node.js Internals 🚀 Just wrapped up an intensive session on Node.js Internals, and it’s fascinating to see what happens under the hood! Today’s focus was the architecture that makes Node.js so efficient. I spent time deconstructing: - Main Thread Execution: How the process starts and the initial script execution flow. - The Event Loop Phases: Getting into the nitty-gritty of expired timers/callbacks, I/O polling, and setImmediate. - Order of Operations: Understanding exactly how the runtime prioritizes tasks to keep the application non-blocking. There is still so much to uncover in the world of system design and asynchronous runtimes, but today’s deep dive provided a solid foundation. Onwards to more learning! 📈 A huge shoutout to the mentors for making these complex concepts so digestible: Piyush Garg | Hitesh Choudhary | Anirudh Jwala | Akash Kadlag #NodeJS #WebDevelopment #Backend #EventLoop #CodingJourney #ChaiCode #LearnInPublic

I once had a bug where my callbacks were firing in the wrong order. Spent hours on it. Turns out I had no idea how Node.js actually schedules things. So I read the official docs from start to finish. Here's the whole picture 👇 𝗡𝗼𝗱𝗲.𝗷𝘀 𝗻𝗲𝘃𝗲𝗿 𝘀𝗶𝘁𝘀 𝗮𝗻𝗱 𝘄𝗮𝗶𝘁𝘀. When you read a file, Node doesn't freeze and stare at the disk. It says "I'll come back when it's ready" and goes off handling other things. That's the Event Loop. It's basically a todo list manager that keeps spinning. 𝗧𝗵𝗲 𝗹𝗼𝗼𝗽 𝗵𝗮𝘀 𝟲 𝗽𝗵𝗮𝘀𝗲𝘀, 𝗲𝘃𝗲𝗿𝘆 𝘀𝗶𝗻𝗴𝗹𝗲 𝗿𝗼𝘁𝗮𝘁𝗶𝗼𝗻: 1. Timers⏱️: runs setTimeout / setInterval callbacks 2. Pending🔃: handles I/O errors from last round 3. Idle🏠: internal Node housekeeping (you can't touch this) 4. Poll📁 : the big one, waits for new I/O events. This is where Node spends most of its life 5. Check✅: runs setImmediate callbacks 6. Close🔒:handles things like socket.close() And before moving between ANY of these phases? It drains the microtask queue first (process.nextTick → Promises). 𝗢𝗻𝗲 𝘁𝗵𝗶𝗻𝗴 𝘁𝗵𝗮𝘁 𝘀𝘂𝗿𝗽𝗿𝗶𝘀𝗲𝗱 𝗺𝗲 𝘁𝗵𝗲 𝗺𝗼𝘀𝘁: setTimeout(fn, 0) is NOT actually 0ms. libuv (the engine under Node ie basically a C library.) secretly converts 0 → 1ms. Meanwhile, setImmediate doesn't care about time at all. It just fires after the Poll phase. Every time. No race. No clock. So if you write both in the same script: → Sometimes setTimeout wins → Sometimes setImmediate wins → It depends on how fast your machine booted that loop But inside an I/O callback? setImmediate wins. Always. Guaranteed. 𝗧𝗵𝗲 𝗿𝗲𝗮𝗹 𝘁𝗮𝗸𝗲𝗮𝘄𝗮𝘆: It's one loop, six phases, and a very smart way of never blocking. If you write Node code without knowing this, you're driving with your eyes closed. Have you ever been burned by unexpected async order in Node? Drop it in the comments 👇 #nodejs #javascript #webdevelopment #backend #softwareengineering

This week wasn’t just about writing code — it was about understanding what actually happens behind it. Instead of jumping straight into frameworks, I focused on the fundamentals that power everything. 📚 Here’s what I explored this week: 🧠 𝗡𝗼𝗱𝗲.𝗷𝘀 𝗜𝗻𝘁𝗲𝗿𝗻𝗮𝗹𝘀 – How Node.js runs on a single main thread – What actually happens when we run node filename.js – Event Loop phases (timers → IO → callbacks → close) – Why setTimeout can execute before file operations – Blocking vs non-blocking code – How libuv + thread pool handles heavy tasks behind the scenes ⚙️ 𝗘𝘅𝗽𝗿𝗲𝘀𝘀 & 𝗔𝗣𝗜𝘀 – Setting up a basic server using Express – Middleware (express.json()) and why it matters – Creating routes and handling requests/responses – Understanding serialization & deserialization – Thinking in terms of APIs instead of just functions 🖥️ 𝗗𝗢𝗠 & 𝗘𝘃𝗲𝗻𝘁 𝗦𝘆𝘀𝘁𝗲𝗺 – Why inline events are not scalable – Deep dive into addEventListener() – Event bubbling vs capturing – Event phases: capturing → target → bubbling – Event delegation for cleaner and scalable code 🛠️ 𝗪𝗵𝗮𝘁 𝗜 𝗯𝘂𝗶𝗹𝘁 𝘁𝗵𝗶𝘀 𝘄𝗲𝗲𝗸: – 𝗠𝗼𝘃𝗶𝗲 𝗗𝗲𝗰𝗶𝘀𝗶𝗼𝗻 𝗔𝗽𝗽 → Fetching data from API and dynamically updating the UI – 𝗞𝗮𝗻𝗯𝗮𝗻 𝗕𝗼𝗮𝗿𝗱 → Implemented drag & drop using proper event handling 𝗚𝗶𝘁𝗵𝘂𝗯 𝗿𝗲𝗽𝗼: https://lnkd.in/gE65dw-V Built these to actually apply concepts like event flow, async behavior, and DOM manipulation. 💭 𝗞𝗲𝘆 𝘁𝗮𝗸𝗲𝗮𝘄𝗮𝘆: I used to just use APIs, event listeners, or async code… Now I’m starting to understand how they actually work under the hood. And that’s changing how I think while writing code. Still a long way to go — but this week felt like moving from just coding → to actually thinking like a developer. Thanks to.. Hitesh Choudhary Piyush Garg Suraj Kumar Jha Akash Kadlag Jay Kadlag sir... #chaicode #NodeJS #JavaScript #WebDevelopment #Backend #DOM #LearningJourney #PlacementPrep

Just finished writing a deep dive blog on Node.js Architecture. Click Here 👉👉: https://lnkd.in/gsXv-rdg For the longest time, my understanding of Node.js was very simple: Node.js = JavaScript running on the V8 engine. And honestly, if someone had asked me this a month ago, I probably would have given the same answer. But once I started exploring the internals of Node.js, I realized how much more is happening behind the scenes. The deeper I went, the more fascinating it became. Node.js isn’t just V8. It’s a combination of multiple components working together: • V8 Engine – executes JavaScript • libuv – handles asynchronous I/O • Event Loop – coordinates execution • Thread Pool – processes background tasks • Node APIs – bridge JavaScript with system operations All of these pieces together create the non-blocking, event-driven architecture that makes Node.js so powerful for building scalable backend systems. I tried breaking down these concepts in a simple way in my latest blog, along with clearing some common misconceptions about Node.js. What started as curiosity quickly turned into genuine fascination with the engineering behind it. Learning a lot through the cohort and the community. #NodeJS #JavaScript #BackendDevelopment #SystemDesign #LearningInPublic #Chaicode Special thanks to the amazing mentors and community: Hitesh Choudhary Piyush Garg Chai Aur Code Akash Kadlag Suraj Kumar Jha

🚨 I thought TypeScript was overrated… until I realized I was using it wrong At first — I loved it. Then — I hated it. Now — I finally understand it. When I started using TypeScript in real projects, it felt like things got worse: harder to read harder to maintain more friction than value For a long time I thought: 👉 “TypeScript is overhyped and makes real projects worse.” I was wrong. 💡 The turning point I joined a project where TypeScript just worked. Clean. Readable. Predictable. That’s when I realized: The problem wasn’t TypeScript. The problem was how we used it. ❌ What went wrong 1. Types mixed with logic Huge inline types + deep destructuring = unreadable code 👉 Extract types. Name things. 2. Types as API contract Works only in fullstack TS (e.g. Next.js) 👉 Otherwise: types ≠ runtime validation 3. Fake type safety any, as, @ts-ignore everywhere 👉 At that point TS becomes decoration 4. Mindset issues Blaming JS for no types while praising Python for the same thing 👉 leads to inconsistent decisions ✅ What I believe now TypeScript is just a tool. Used well: ✔ reduces bugs ✔ improves readability Used poorly: 👉 slows you down and adds complexity 🔑 The real lesson TypeScript doesn’t fix architecture. It amplifies it. What was your journey with TypeScript? #typescript #javascript #react #frontend #webdevelopment #softwareengineering #programming #cleanCode #architecture #developers

⚠️ Something I realized after writing a lot of code Most of the time… the problem isn’t the code. It’s: unclear requirements rushed decisions poor structure assumptions we didn’t question As developers, we love to jump into coding. But the real impact comes from thinking before typing. I’ve seen simple code work better than complex solutions just because the problem was understood properly. The best engineers don’t just write code. They reduce confusion. Less confusion = fewer bugs Fewer bugs = better systems What do you think causes more issues in projects? 👉 Bad code 👉 Or unclear thinking #SoftwareEngineering #DeveloperMindset #ProblemSolving #BackendDevelopment #EngineeringMindset #CleanArchitecture #TechCareers #BuildInPublic #NodeJS #NestJS