Not really a "high volume" site but I used it as the main database for a community site with about 200k pageviews per month for several years. Unsurprisingly, it was fine given that's a pageview every 10 seconds or so.

Yet even at that level we eventually ran into some repeating file corruption and locking issues that confused me enough to eventually migrate it to Postgres and chuck it up on Heroku to stop bothering with it.