If you're going to scale up to 10s of millions of inserts a day and 100s of billions of rows, I recommend MySQL as a step on a journey towards Vitess. Otherwise

If you're going to scale up to 10s of millions of inserts a day and 100s of billions of rows, I recommend MySQL as a step on a journey towards Vitess. Otherwise, I recommend Postgres. For anything other than a data-oriented startup, I'd pick Postgres all day long. The troubles each database gives you do have different flavours. Postgres's query planning is mercurial and sometimes quixotic. It can be tedious forcing it to do the right thing, and it does sometimes switch strategy resulting in queries taking 100x or more longer than they used to, just because some stats changed. MySQL's query planner is more stupid, more predictable, and less likely to give you this kind of pain. OTOH you have to be more careful writing queries and you sometimes end up adding hints or encoding a query structure which locks in a query plan which might not be the best one long term. But it usually degrades gradually rather than suddenly. I'm not sure which is worse, though, because gradual degradation doesn't demand fixing.