If you can't afford database people, pick the database that you have the most experience with. The databases you mentioned (MySQL, Postgres, and SQL Server) are

If you can't afford database people, pick the database that you have the most experience with. The databases you mentioned (MySQL, Postgres, and SQL Server) are all good enough for most projects - as long as you know how to use one of them. Generally, though, it's a bad idea to pick a database that you don't understand, thinking that the database is somehow "better." A good musician can make a bad instrument sound good, but a bad musician isn't helped by playing a Stradivarius: your knowledge is the better differentiator than the instrument quality. If you're one person doing side projects, I'd also strongly recommend a managed database as a service. If you're not trying to become a database administrator, then every hour spent managing databases is distracting you from producing the value that will bring you customers. Customers don't pay you for your database management skills: they pay you for the value your app produces. Focus on the app code and its value, not testing your database restores.