Easy Learn
A complete, beginner-to-production system design walkthrough for handling supplier inventory feed delays and failures without ever overselling: circuit breakers, safety stock buffers, Kafka-backed ingestion pipelines, reservation with optimistic locking, reconciliation jobs, and end-to-end monitoring, illustrated with inline architecture and sequence diagrams and Java code.
Designing a Transaction Reconciliation System How do you prove, every single day, that millions of transactions your platform says happened actually match what the banks say happened — without losing a single rupee, dollar or cent and without a human reading every row? 01 · Intro & History02 · Problem03…
Designing a Spam Link Detection & Prevention System A production-grade blueprint for catching and stopping malicious and unwanted links across billions of daily direct messages and comments — without slowing down a single legitimate conversation. 01 · Intro & History02 · Problem03 · Core Concepts04 · Architecture05 · Internals06 ·…
Designing a Checkout Abandonment Recovery System A complete, from-scratch walkthrough of how large e-commerce platforms detect abandoned shopping carts and automatically re-engage customers to bring them back to complete their purchase — covering architecture, data flow, scaling, reliability, security and real production patterns used by companies like Amazon, Flipkart and…
A complete, beginner-to-production system design walkthrough for a real-time checkout A/B testing platform: deterministic edge-resolved bucketing, async Kafka-backed event ingestion, sequential-testing-safe statistics, guardrail-driven auto kill switches, and everything else needed to safely measure the effect of checkout-flow variants at a million-plus requests per minute without ever slowing checkout down.
Designing a Card-Testing Botnet Fraud Detection System A production-grade, interview-ready deep dive into stopping card-not-present (CNP) fraud where a botnet hammers your payment gateway with thousands of stolen card numbers simultaneously — while staying fast, fair to legitimate customers, and resilient at a million requests per minute. 01 · Intro…
A complete, beginner-to-production system design walkthrough for a bulk payroll payment processing system that pays 50,000 employees the correct amount, exactly once, every pay period — using idempotency keys, the Saga pattern, the outbox pattern, chunk-level checkpointing, and banking-rail reconciliation at platform scale.
Designing a “Buy Online, Pick Up In Store” (BOPIS) System A complete system design walkthrough for coordinating real-time inventory between an online marketplace and thousands of physical store locations — built to survive a million requests a minute. 01 · Intro & History02 · Problem03 · Core Concepts04 · Architecture05…
Designing a Multi-Touch Affiliate & Referral Attribution System How marketplaces like Amazon, Flipkart, Uber, and Airbnb track every click a referrer generates, follow a customer across days or weeks of browsing, and fairly decide who gets paid when a sale finally happens — explained plainly enough for a first-week engineer,…
Designing a Buy Now, Pay Later (BNPL) System with Real-Time Credit Decisioning A complete, from-first-principles walkthrough of how to architect a marketplace financing feature that lets a customer split a purchase into instalments, with a credit decision returned in real time, at checkout, without breaking the shopping experience. 01 ·…