Designing High‑Concurrency Flash Sale (秒杀) System Architecture

Flash sale (秒杀) is a common e‑commerce marketing technique that sells a limited quantity of products at extremely low prices during a short, predefined time window, generating hype but causing traffic that can be hundreds or thousands of times higher than normal, which stresses the website’s technical infrastructure.

Technical challenges include: (1) disruption to existing site services; (2) extreme load on application servers and databases due to continuous page refreshes; (3) sudden surge in network and server bandwidth; and (4) the risk of users obtaining the order‑submission URL before the sale starts.

Response strategies are to deploy the flash‑sale system independently from the main site, render the product page as a static file to avoid application‑server processing, lease additional bandwidth and cache static pages via CDN, and generate order‑submission URLs dynamically with server‑side random parameters that become valid only when the sale begins.

System architecture design emphasizes a minimalistic page: a single‑item order form, default address and payment settings, and only the first successful order is forwarded to the order subsystem while subsequent users see a “sale ended” page. Button activation is controlled by a tiny JavaScript file that is refreshed at the start of the sale; the file is served with a random version number and is not cached by browsers or CDNs.

Order submission control can be achieved by limiting the number of requests each order‑server handles (e.g., 10 servers each accepting up to 10 requests). The overall architecture is illustrated by the following diagrams:

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