In absolute terms, Postgres has more features and has been used at scale by Instagram, etc. while MySQL has a much bigger user base and has been used at scale by likes of Facebook, Quora, etc.
But how about in combination with NodeJS?<p>Which is 1) more popular, 2) easier to setup, and 3) better for scaling out (not up)?
Are you using a specific back end framework or just plan old node?<p>I generally don't ask questions about databases like you are here but I have used both mysql and postgres with large node projects (as well as others!).<p>Popular: I would say this feels like a toss up. Both are pretty popular. I think they go back and forth on pure popularity. Both have strong communities. Mysql is "owned" by oracle so I guess you can take that into the popularity equation.<p>Easy to set up: again, a toss up. Both are relatively easy to set up initially. Both have a huge number of optional configurations depending on your needs. Anecdotally, mysql has a lot of engine options depending on needs. Out of the box, they are fairly similar on setup. Also fairly similar on node setup and configuration.<p>Scaling out: these are both RDBMS systems so scaling out is always an adventure. This has little to do with node and a ton more to do with your scaling needs. Both have the capability. Neither is easy.