Introduction to Not Only SQL

PostgreSQL is a solid ACID relational database management system and uses the SQL language to process, manage, and query the data. Its main purpose is to guarantee a consistent view of a business as a whole at all times while applications are concurrently active in reading and writing modes of operation.

To achieve a strong level of consistency, PostgreSQL needs the application designers to also design a solid data model and, at times, to think about concurrency issues.

Million users issue

In recent years, big players in the industry faced a new scale of business never before seen. Nowadays, a big player may have tens or hundreds of millions of concurrent users. Each user produces new data, and some business models need to react quickly to the newly inserted data and make it available to customers—mostly advertising networks.

Solving that scale of activity introduced new challenges and the necessity to work in a distributed fashion. A single instance would never be able to address hundreds of millions of concurrent users, all actively producing data.