Via Zack, there's an interesting entry on Xooglers from an engineer on the Google AdWords team, about the experience of using MySQL initially and then switching to an unnamed commercial database. (Of course, there is the usual uninformed proselytizing in the comments: "you should have used x, idiots!")
Two impressions from the story:
- MySQL works just fine for a lot of applications. While admittedly I often speak with pro-Postgres people, there's a segment of the user base that has come to regard using MySQL in almost any situation as something to be embarrassed about. I've never understood that attitude (or why SQLite is not regarded in the same way): there are many applications for which MySQL is a good choice or even the best choice. AdWords may well be one of them—I won't claim to know.
- Technical decisions made at the insistence of management often end badly:
After AdWords launched, Jane, the ads group manager, decided that now would be a good time to switch over to a "real" database. "Real" is one of those words that Doug ought to add to his list of words. It means "expensive". Many managers seem to have this idea that it is invariably true that you get what you pay for, and that therefore nothing that is available for free can possibly be any good....
To make a long story short, it was an unmitigated disaster.