I have learned this while working in the industry: there are so many databases, and the database choice that you are going to make will influence your whole business. It will influence how do you structure your codebase, how do you store your customer data and the performance of your whole system.
You can ask yourself “can’t there be one database which is the best of everyone else?” and all the DBAs in the world would reply you with “no”. Store and retrieve data is one of the most complex and crucial parts of your codebase, and if you want to store files like Dropbox or emails like Gmail or payment transactions like PayPal, the needs are completely different, hence why there are multiple databases and each solves one of this problem.
What is the best choice? It’s to think upfront about your pattern and how you would store and retrieve data from the database, then try few alternatives and test each one with some production traffic/data (you don’t want to test it only with a small subset, because you may find a lot of performance problem in the future). Also, it’s important to understand at least a bit how the database stores the information, to make sure that the database guarantees the correctness of the data. You don’t want to have corrupted data after some time because you haven’t thought about it upfront.
This problem is very true also in big companies, and AWS provides multiple database solutions according to your use case. This article by Werner Vogels (CTO of Amazon) explains some of the alternatives and options you can find on AWS and evaluate which one is best for your use case.