The document is a presentation about scaling applications with Symfony. It discusses concepts related to scalability like load balancing and sharding. It provides advice on profiling code to diagnose bottlenecks and optimizing aspects like caching, databases, and front-end performance. Specific technologies discussed include APC, Zend Opcache, Memcached, Redis, MySQL, and NoSQL databases. Real-world examples of large applications built with Symfony like a social game with millions of daily users are also presented.