Advanced MySQL Question - Retrieving Similar Items Based on Tags

[eluser]bretticus[/eluser]
Yeah, I think amazon throws more machinery at it. They are probably not using PHP or MySQL either. Neither of which seem to scale well. 3.8 million records is A LOT to query against. I know there are some other database engines that automatically optimize large tables (like mongo), but I have nothing noteworthy to share about your problem tonight. I have *heard* postgres handles large tables better than MySQL. Poor suggestion though.

Good luck!