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Designing a System to Catch a Price Gone Wrong Before It Goes Viral A complete, from-scratch architecture for detecting anomalously low product prices — whether a fat-fingered seller mistake or a deliberate pricing attack — before an army of bargain hunters can place ten thousand orders on a $4,999 television…
A production-grade system-design walkthrough for subscription-box e-commerce: staggered recurring billing with idempotency keys, dunning with exponential backoff, preference-driven curation as constraint satisfaction, atomic optimistic inventory reservation, event-driven saga (billing → curation → fulfilment) over per-subscriber Kafka partitions, cutoff-aware APIs, PCI tokenisation at the gateway boundary, three-way reconciliation, and shadow →…
Designing a real-time credit approval system for Buy-Now-Pay-Later (BNPL) A deep, from-first-principles walkthrough of how to design a BNPL platform that decides — in a few hundred milliseconds — whether to approve a shopper’s installment plan at the checkout of a partner e-commerce site, at a scale of millions of…
Detecting account sharing and credential leaks before they turn into a breach A ground-up, beginner-friendly system design walkthrough of how large platforms build the pipelines, models, graph databases, and streaming infrastructure that spot one account being used from two continents at once — and decide, in milliseconds, what to do…
A production-grade system-design walkthrough for absorbing a 50x, 48-hour Black Friday traffic spike: predictive pre-scaling and horizontal auto-scaling, virtual waiting rooms for graceful load shedding, circuit breakers and bulkheads around the payment gateway, atomic conditional inventory decrement, a Kafka-buffered async order pipeline, layered CDN+cache+read-replica offload protecting the primary database, and…
Designing “Who Viewed Your Profile” with near real-time updates A full walkthrough of how professional networking platforms track, aggregate and surface profile-view activity — near-instantly, at hundreds of millions of users, without drowning the system in write traffic. 01 · History02 · Problem03 · Capacity04 · Architecture05 · Capture06 ·…
Designing a Dynamic Pricing System A from-first-principles walkthrough of how large e-commerce and marketplace platforms adjust prices in near real time from demand, live inventory, and competitor pricing — architecture, data flow, scaling, reliability, and security. 01 · Intro02 · Problem03 · Concepts04 · Architecture05 · Internals06 · Algorithms07 ·…
A production-grade system-design walkthrough for detecting compromised public-figure accounts from anomalous posting behaviour: per-account behavioural baselining across temporal, content, session, and interaction features; ensemble risk scoring with high-confidence rule overrides; a tiered response ladder (passive log → flag → step-up auth → temporary hold and page); human-in-the-loop review; and fail-toward-caution…
Designing for a viral post: handling 10 million views in one hour without taking the rest of the platform down A beginner-friendly, step-by-step system design walkthrough of how large-scale platforms detect, absorb, and isolate a sudden hot-key traffic spike — the kind that happens when one post, tweet, or video suddenly…
Designing a system that spots viral content before the crowd does A complete, ground-up walkthrough of how to build a platform that watches engagement signals as they happen and flags posts that are about to explode — minutes or hours before a human would ever notice. 01 · Why It…