Greenfield webapp data storage decision tree

I saw a discussion about storing data in one of my slack channels and saw a line too good to leave in the slack.

Here’s a data storage decision tree for 95% of applications. Do you have data to durably store?

1. Use an open source relational database

(The original poster specified PostgreSQL, but MySQL/MariaDB are viable alternatives in my mind. Each has different strengths.)

The modern, open source RDBMS is flexible and scaleable (even web scale [warning, video has cursing]). It’s free from licensing fees (though you can pay for support). There are turnkey solutions for managing it in the cloud. There are plenty of developers who know how to use it (even more developers know how to use SQL) and many DBAs and sysadmins who know how to tune it. . You can scale it out by using read replicas and scale up by buying better hardware (or VMs). Every language has a library that talks to RDBMS. The database will maintain data integrity. Many tools that non technical users favor can connect to them (even Excel, if you install the right ODBC driver).

There are plenty of other solutions out there (filesystem, no SQL variants, xml databases, data lakes). They exist for a reason. For certain problems and at certain scale they are better solutions than the Swiss army knife of a RDBMS. But the default decision should always be an RDBMS, and the onus should be on the other solution to justify its present. For 95% of problems, the your default should be MySQL/MariaDB or Postgres.