[rshao]

I totally agree. Regex gets easier and easier as you do more. It's just hard to do in the beginning (personally I started with trial and error).

But definitely, robust database design is among the hardest things I've had to do. I mean, it's one thing to just set up a couple of tables and write queries to get your desired data. It's a whole different ball game to ensure that it'll be scalable, and designing with consideration that you'll eventually have to split your database into shards as it grows.

In a way, it's a subcategory of what I think is the hardest thing, which is designing for scalability. Just because something works with a handful of users doesn't mean it'll work when you have millions of users and hundreds of simultaneous connections, which most of us are striving for.