Any kind of data can be stored in any kind of database. The main problem comes from inefficiency in space, retrievals, or speed of operations, and the importance of these depends on how the data is used. Some of the real value in graphs comes from being able to make connections, which means doing joins. MongoDB is not good for this.

thank you quoll for your help, MongoDB has lookup and after MongoDB 6 works even if both collections are sharded, but i guess for fast triplestore you need graph database