It's a good thing I favorited this. System design doe beginner. https://news.ycombinator.com/item?id=23904000

Also, check the benchmark, the scalability, the architecture, etc. Sometimes, DB with similar frontend (API) are very different on the backend (architecture, implementation), for example CockroachDB vs PostgreSQL, hence different usage. One is OLTP, the other is OLAP, etc.