Idiots are a Lot Smarter
Simon Willison (et al.) took some nice notes on a talk by Josh Schachter, developer of del.icio.us. Speaking from my experience developing web applications at Amazon.com and Six Apart, I agree with every one of these points. A lot of these are easy no-brainers that lots of web apps don't get right—like dropping users back where they were after registering.
Some particularly nice tidbits:
Scaling: avoid early optimization. SQL doesn't map well to these problems—think about how to split up data over multiple machines. Understand indexing strategies, profile every SQL statement. Nagios or similar for monitoring.
There's no explanation what "these" problems are. Still, I think it's the right sentiment. The relational model is a weird model that was foisted on computing decades ago. It's become a crutch that developers—and particularly web developers—rely on excessively.
"Idiots are a lot smarter than you"—wait to see what breaks before you fix it.
There's little I hate more in engineering that attempts to fix unbroken stuff. Christopher Alexander's best line is, "Every act of building is an act of repair." We're here to make the world better, only.