I frankly don't know much about unix locking, and you are right, but have written concurrent production code in major apps for major players. What I was saying is that you don't need table locking on the database (that has its own uses), you just want to have a mutex access to a pool of resources, and the database does that excellently. And if you add a datetime field that you happen to update with the update, you can know who locked what and easily inspect it externally. And this is definitely a plus when running concurrent stuff, where bugs are rather hard to detect.