Deciding on a database to use

The first decision to make is what type of database to use, such as a relational (SQL) database, a schemaless document database, a key-value database, a graph database, or a more specialized database such as a time-series database. If you value your data at all and your database has any structure at all, a schemaless document database is usually a poor choice that you will end up regretting later when you discover anomalies in your data, far too late to fix them. Most key-value databases are too limited for the use of structured data unless they are treated as document databases, in which case they have the same issues as document databases. Unless you have studied and have had experience with graph databases and are sure they are the best database type for your application, they probably aren't. Similarly, unless you have very specialized needs, a specialized database such as a time series database is probably the wrong choice for your application...