Web Server Load Balancing with NGINX Plus


PBS (Public Broadcasting Service) is made up of more than 350 local public noncommercial TV stations in all 50 states, Puerto Rico, U.S. Virgin Islands, Guam and American Samoa. It is America’s largest classroom, the nation’s largest stage for the arts, and a trusted window to the world.


As new episodes of the period drama Downton Abbey aired, more viewers became interested, and more users arrived at PBS’ website. As a result, PBS has two distinct traffic patterns: a reliable daily video view number that generally remains constant, and the Downton Abbey season numbers, which can increase video traffic as much as six times that of a normal day. This period typically lasts as long as the new season is running.

This pattern is known as the “Thundering Herd,” where traffic increases dramatically for a predictable period of time, then returns to normal almost overnight. With streaming video requests coming in fast and furious, web traffic and web application performance can suffer as users flood the site to see the newest episode or read the latest information on this popular show.


The benefits we get from NGINX are speed and reliability. It’s our firewall, cache, and proxy. It fronts our APIs and our public‑facing websites. Pretty much every request that goes to or its subdomains runs through NGINX. Really the biggest reason we use NGINX is to mitigate thundering herd and improve our application performance.
– Mike Howsden, Director of DevOps at PBS

NGINX offers highly scalable traffic routing, securing, and caching capabilities, all of which combine to provide a single point of service for high‑traffic websites and web applications. Using NGINX’s caching and proxying capabilities, PBS is able to serve its thundering herds of traffic quickly and without touching backend systems.

One feature that allows NGINX to serve such large amounts of traffic without bothering backend systems is the ability of the proxy cache to use stale information. That means serving a cached version of the PBS site and its contents directly from NGINX, completely removing the database and other backend systems from the equation. Special, more unique requests still pass through to the server, but NGINX ensures that users are almost entirely served their content directly from a highly optimized, in‑memory cache which has been optimized over a decade to be the fastest possible source of web content.

In fact, says Howsden, you can actually see NGINX at work, a bit like watching a finely honed assembly line from the manager’s office. “My favorite thing is running curl commands against an NGINX web server, tailing the access log, and just watching all these super fast requests coming through, and then seeing the one slow request that makes it to the backend server, like when I’m using ‘proxy cache use stale updating’. Watching that phenomenon happen and seeing just how much traffic it can handle and not even care… Access logs are just pouring down the screen, and NGINX just does not care. It’s been very useful in my career for scaling dynamic web applications.”

About PBS

The Public Broadcasting Service is a national broadcast network with over 350 affiliates, and hundreds of unique shows. With popular series such as Downton Abbey, Frontline, Nature, and Nova, PBS is viewed in over 80% of American households. Each month, viewers watch over 250 million videos on PBS’ Web, mobile, and connected device platforms, and the PBS websites receive an average of 15.3 million unique views.


“Thundering Herd,” where traffic increases dramatically for a predictable period of time, then returns to normal almost over night.


PBS is a national broadcast network with more than 350 affiliates.

Arlington, Virginia
Founded in 1969
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