Relational databases have become popular because of their flexibility and that has not changed much through the decades. You can combine, aggregate, filter your

Relational databases have become popular because of their flexibility and that has not changed much through the decades. You can combine, aggregate, filter your data, tell the RDBMS in which shape you want it back, and speed up processing with the right indexes. And if you normalize your data properly, you can be confident that you won't end up with a pile of mud one day. Other databases like column oriented ones, or key-value dbms may be better at niche use cases like analytics, caching or very write heavy applications. A social network is mainly about simple CRUD and combining data in various ways, so it is primarily a matter of taste which RDBMS you use. So you should probably stick to what you know best.