Why not? I've worked with a database where we needed to join more than double that on some common queries, in part because financial stuff tends to touch severa

Why not? I've worked with a database where we needed to join more than double that on some common queries, in part because financial stuff tends to touch several other business domains at once. The explains can be hairy at first but once you've started systematically analysing a query and know some of the quirks of the MySQL query planner you'll manage to identify missing indices and squeeze out very, very good performance. That was a database where we had warm tables bigger than fifty million rows. I personally migrated it from single instance MySQL 5 to a MySQL 8 clustered rig and optimised hundreds of queries written by people learning basics on the job, going from horrifying to very reasonable latencies as seen from the web clients.