Jeremy Edberg, the first paid employee at reddit, teaches us a lot about how to create a successful social site in a really good talk he gave at the RAMP conference. Watch it here at Scaling Reddit from 1 Million to 1 Billion–Pitfalls and Lessons.

Jeremy uses a virtue and sin approach. Examples of the mistakes made in scaling reddit are shared and it turns out they did a lot of good stuff too. Somewhat of a shocker is that Jeremy is now a Reliability Architect at Netflix, so we get a little Netflix perspective thrown in for free.

Some of the lessons that stood out most for me: 

• Think of SSDs as cheap RAM, not expensive disk. When reddit moved from spinning disks to SSDs for the database the number of servers was reduced from 12 to 1 with a ton of headroom. SSDs are 4x more expensive but you get 16x the performance. Worth the cost. 
• Give users a little bit of power, see what they do with it, and turn the good stuff into features. One of the biggest revelations for me was how much reddit learns from its users and how much it relies on users to make the site run smoothly. Users are going to tell you a lot of things you don’t know. For example, reddit gold started as a joke in the community. They made it a product and users love it.
• It’s not necessary to build a scalable architecture from the start. You don’t know what your feature set will be when you start out so you want know what your scaling problems will be. Wait until your site grows so you can learn where your scaling problems are going to be.
• Treat nonlogged in users as second class citizens.  By always giving logged out always cached content Akamai bears the brunt for reddit’s traffic. Huge performance improvement. 

There's lots more. Here's my gloss of the talk where we learn many lessons from the mistakes made in the early days of scaling reddit: