System Design
Browse all articles, tutorials, and guides about System Design
Posts
How Netflix Ships a Third of the Internet: The CDN They Had to Build
At its 2015 peak Netflix was 37% of North American downstream traffic, and almost none of it came from a commercial CDN. Open Connect is a cache hierarchy built on one asymmetry: Netflix knows tonight what people will watch tomorrow. Here is how the appliances, the nightly fill, the BGP steering and the 800 Gb/s FreeBSD boxes fit together, a runnable comparison of push fill against pull-through caching, and what it teaches anyone running a cache.
In-App, Email and Push From One Event
An order ships. The user wants a badge in the app, a digest email later, no push at all, and their own webhook endpoint pinged. The design that handles that without duplicates: an outbox keyed by event, user and channel, preferences evaluated at send time, digest windows, and provider feedback wired back in. With a runnable model and a build-or-buy verdict.
Meta Says Every Muse User Gets Their Own VM
Meta says its new consumer agent runs on a dedicated cloud VM per person, with a second agent that has to approve anything leaving that machine and a credential store the agent can use but never read. Those are three infrastructure decisions you face too. Here is what each one defends against, what it costs to build, and a runnable model of the broker, including the injected page that tries to walk out with a token.
How Stripe Avoids Double-Charging Anyone
A payment request times out. Did the charge happen? Stripe answers that question with idempotency keys, and the design behind them is more than a cache of responses: locked key rows, recovery points, and a rule about which calls can be retried. Here is the design, a working Postgres implementation, the run where our own version double-created rides, and the constraint that caught it.
How Does It Work So Fast? The Engineering Behind Instant UI Responses
Credit card validation, username checks, autocomplete, URL shorteners - they all feel instant. Here is what is actually happening under the hood in each case.