If you've got a database you can fit in memory that's got very sporadic access pattern it could be a nice boost even on SSDs. My biggest personal project has a 15GB database on disk, all of it a single table of 7.5M comments and a PGroonga full text search index. The queries are very disproportionately searching for low frequency terms so the index will largely cached, but most of the rows will require disk access. Since I can spare the ram to get the entire db in memory it's a clear win for me even if it's decent speed without. My users are basically a font of random accesses and being able to treat PostgreSQL as an in-memory db is convenient.
Comments
If you've got a database you can fit in memory that's got very sporadic access pattern it could be a nice boost even on SSDs. My biggest personal project has a 15GB database on disk, all of it a single table of 7.5M comments and a PGroonga full text search index. The queries are very disproportionately searching for low frequency terms so the index will largely cached, but most of the rows will require disk access. Since I can spare the ram to get the entire db in memory it's a clear win for me even if it's decent speed without. My users are basically a font of random accesses and being able to treat PostgreSQL as an in-memory db is convenient.