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• Design a Video Player Frontend (HLS and Adaptive Bitrate)Frontend · A plain-English guide to designing a video streaming frontend: HLS playlists, adaptive bitrate, buffer limits and fast startup, shown on one running example of a streaming app used on slow mobile networks.25 min read · Updated 21 Oct 2026
• Vision-Language Models Explained: How AI Sees ImagesAI and GenAI · A plain-English guide to how vision-language models turn photos into tokens, learn to match pictures and words, describe images, and fail, built on one running shelf-audit example.24 min read · Updated 21 Oct 2026
• Voice Assistant System Design: Speech In, Speech OutAI and GenAI · A plain-English guide to designing a phone voice assistant, from speech-to-text to the model to text-to-speech, built on one running example of a Hindi farmers' helpline.27 min read · Updated 21 Oct 2026
• Web Agents: How Browser-Using AI Agents WorkAI and GenAI · A plain-English guide to web agent design: how a browser agent sees pages, clicks the right element, keeps login state and stays safe, shown on one running example of a form-filling service.25 min read · Updated 21 Oct 2026
• Design a Web Crawler: Politeness, Dedup and the URL FrontierSystem design · A plain-English guide to web crawler system design: the URL frontier, politeness rules and de-duplication, shown on one running example of an Indian-language search engine.27 min read · Updated 21 Oct 2026
• How ZooKeeper Works: Znodes, Watches and ZABSystem design · A plain-English guide to how ZooKeeper works, from znodes and watches to leader election and the ZAB protocol, built on one running batch-job scheduler example.25 min read · Updated 21 Oct 2026
• Labeling and Active Learning: Ask Where the Model Is UnsureAI and GenAI · A plain-English guide to active learning and data labelling: the model picks the examples it is least sure about for experts to label, built on one running crop-disease app example.23 min read · Updated 20 Oct 2026
• AI Agent Sandboxing Explained: How to Contain Agents That Run CodeAI and GenAI · A plain-English guide to AI agent sandboxing after CERT-In's October 2026 advisory: containers vs gVisor vs microVMs, egress control, short-lived credentials, tamper-resistant logs and kill switches, shown on one running example of a coding agent that fixes flaky tests.22 min read · Updated 20 Oct 2026
• AI Decision Models Explained: Typed Choices Instead of Generated TextAI and GenAI · A plain-English guide to AI decision models: picking one allowed option with probabilities, running them locally and setting thresholds, shown on one running example of a grocery app's support inbox.20 min read · Updated 20 Oct 2026
• LLD: Design an ATM, With Transactions and Failure StatesSystem design · A beginner-friendly low-level design of an ATM in Java, covering classes, states, the withdrawal flow and every failure state, built on one running example of a white-label ATM fleet.18 min read · Updated 20 Oct 2026
• LLD: Design a Car Rental SystemSystem design · A plain-English guide to car rental LLD: the classes, the date overlap rule, reserving without double booking, states, database guards and one-way trips, shown on one running example of a two-hub rental service.25 min read · Updated 20 Oct 2026
• Chess LLD: Design a Chess Game in Java, Pieces to CheckmateSystem design · A plain-English guide to chess LLD: Java classes for pieces, board, moves, legal-move checks, special moves, draws and perft testing, shown on one running example of an online club chess app.30 min read · Updated 20 Oct 2026
• Class Imbalance: When Fraud Is 1 in 1,000AI and GenAI · A plain-English guide to class imbalance: the right metrics, sampling, class weights and thresholds, built on one running payment fraud screening example.19 min read · Updated 20 Oct 2026
• Cricket Scoreboard LLD: Overs, Wickets and Live Updates in JavaSystem design · A plain-English guide to cricket scoreboard LLD: the Java classes for overs, extras, wickets, strike, undo and live updates, shown on one running example of a gully cricket scoring app.28 min read · Updated 20 Oct 2026
• Docker Hub's October 2026 GhostPat Flaw Explained: When a Token Changes OwnersBackend · A plain-English guide to the Docker Hub GhostPat vulnerability: how converting an account into an organisation passed working tokens to another user and what to check now, shown on one running example of a team's build-server token.18 min read · Updated 20 Oct 2026
• Domain-Driven Design and Bounded Contexts, Explained SimplyBackend · A plain-English guide to domain-driven design and bounded contexts: ubiquitous language, context maps, translation layers and aggregates, shown on one running example of a farm-to-home produce marketplace.27 min read · Updated 20 Oct 2026
• LLD: Design an Elevator SystemSystem design · A plain-English guide to elevator low level design: the classes, the LOOK scheduling rule, the state pattern and a dispatcher in runnable Java, shown on one running example of a two-car tower.20 min read · Updated 20 Oct 2026
• Encryption Basics: Symmetric, Asymmetric and SignaturesBackend · A plain-English guide to encryption basics: what symmetric encryption, asymmetric encryption and digital signatures each protect, shown on one running example of a family document vault.22 min read · Updated 20 Oct 2026
• Exploration vs Exploitation Explained: How Bandits Help RecommendersAI and GenAI · A plain-English guide to the exploration exploitation tradeoff and the bandit algorithms recommenders use to handle it, built on one running short-stories app example.20 min read · Updated 20 Oct 2026
• Apache Flink: Watermarks and Exactly-Once StreamsSystem design · A plain-English guide to Flink watermarks, late events and exactly-once results after a crash, built on one running example of a live city-wide running leaderboard.26 min read · Updated 20 Oct 2026
• Frontend Error Monitoring: Catching Crashes on Millions of PhonesSystem design · A plain-English guide to frontend error monitoring: how apps catch crashes on phones and browsers, send them home, decode them and group them, shown on one running example of a shopping app.26 min read · Updated 20 Oct 2026
• How GFS and HDFS Work: Chunks, One Master, Relaxed RulesSystem design · A plain-English guide to how GFS and HDFS store huge files as replicated chunks under one master, built on one running film archive example.27 min read · Updated 20 Oct 2026
• GitHub's November 2026 Pull Request Target Block Explained: How to Fix WorkflowsBackend · A plain-English guide to GitHub's default block on the pull_request_target trigger from 2 November 2026: what pwn requests are, who is affected and how to fix workflows, shown on one running example of an open-source library's docs preview.20 min read · Updated 20 Oct 2026
• Hotel Management LLD: Rooms, Bookings and BillingSystem design · A plain-English guide to hotel management LLD: the classes, half-open stays, a per-night free-room check, booking states and a Java folio for checkout, shown on one running example of a 60-room hotel.29 min read · Updated 20 Oct 2026