Building Blocks of a Web System

Every web system, however large, is put together from a handful of parts, and each one is there to do a single job. You will meet them one at a time: DNS, which turns a name into an address; the CDN, which serves files from near the reader; the application server, kept stateless so copies of it can come and go; and the database, the one part that cannot be rebuilt. Then you will follow one request through all of them, choose between a relational and a NoSQL database, and learn the two failures a beginner's design most often contains: the N+1 query and the single point of failure. Load balancers and caches appear on the map here and get topics of their own.