History. A long time ago, in the early 90s, there was a database called msql. It was a little DB that used SQL and ran well on low end systems. It was also free

History. A long time ago, in the early 90s, there was a database called msql. It was a little DB that used SQL and ran well on low end systems. It was also free. In fact, it was the ONLY free SQL database out at the time -- that's why it was written. Because of those two advantages (that really only lasted a couple of years), a small ecosystem developed around it. This was the database you used to develop interactive websites in the early/mid-90s. Then MySQL came. MySQL extended mSQL, and kept compatibility with it's ecosystem... and people switched from mSQL to MySQL. Postgres also existed in the 80s and 90s, but it used POSTQUEL, was harder to setup, and had higher system requirements. Not a lot, but enough to discourage use on low end computers. (Remember, Postgres at the time was being developed on university servers, where they had plenty of system resources.) They did address these points in postgre95 (in fact, Postgres adopted SQL as a response to mSQL popularity), but by then it was too late. mSQL and MySQL already had an ecosystem.. and in that brief moment, they lost the race. The idea that it was slower stuck around for many years, even after the improvements in computers, and (less so) optimizations in Postgres made it no longer true. Postgres didn't start being considered again until Go, RoR, et al started to become popular.. displacing the PHP ecosystem. And the biggest reason you see MySQL around so much today is that there's about 25 years of legacy code built around it. Edit: If you're curious what POSTQUEL was like: https://en.wikipedia.org/wiki/QUEL_query_languages https://en.wikipedia.org/wiki/QUEL_query_languages