I really doubt that a schema like that would survive at the kind of scale SW operates at. I'm about 80% sure I saw mention of database operations in the startup/shutdown logs, but I could be misremembering.
My guess is that they bought whatever database software was popular in the early 90s and never changed.
I do know they've been slowly changing the schema over the years, increasing the number of digits in the account number, adding email fields, that kind of thing. But I doubt there's been any major upgrades.
Well early 1990s database sofware wasn't awful. Talking about stuff like Sybase 4.x, roughly equivalent to early MS SQL server, also Oracle, Informix, DB/2, etc. Indexes, query planning (perhaps with hints), cursors, concurrency, were all adequately solved problems by then.
My guess is that they bought whatever database software was popular in the early 90s and never changed.
I do know they've been slowly changing the schema over the years, increasing the number of digits in the account number, adding email fields, that kind of thing. But I doubt there's been any major upgrades.