MemcacheDB looks like a great place to store denormalized subscriptions.

Imagine Kevin Rose, the founder of Digg, who at the time of this presentation had 40,000 followers. If Kevin diggs just once a day that's 40,000 writes. As the most active diggers are the most followed it becomes a huge performance bottleneck. Two problems appear.

You can't update 40,000 follower accounts at once. Fortunately the queuing system we talked about earlier takes care of that.

The second problem is the huge number of writes that happen. Digg has a write problem. If the average user has 100 followers that’s 300 million diggs day. That's 3,000 writes per second, 7GB of storage per day, and 5TB of data spread across 50 to 60 servers.

With such a heavy write load MySQL wasn’t going to work for Digg. That’s where MemcacheDB comes in. In Initial tests on a laptop MemcacheDB was able to handle 15,000 writes a second. MemcacheDB's own benchmark shows it capable of 23,000 writes/second and 64,000 reads/second. At those write rates it's easy to see why Joe was so excited about MemcacheDB's ability to handle their digg deluge.

Posterous has this exact problem when handling subscriptions. We currently denormalize new posts for subscription lists using after_save hooks that translate new posts into new notification records on the backend. But if we can plug this instead into MemcacheDB instead, needless DB writes can be avoided.

How to get Internet Explorer javascript debugging really set up using Visual Web Developer 2008 Express (free version)

I don't know why all the existing articles out there in Internet Explorer javascript debugging always tell you to try the Microsoft Script Editor or other such steaming piles of feces from 2002. Microsoft's Visual Web Developer 2008 at least was released in the last year of the Bush presidency, instead of the beginning of the first term. They GET you by disabling the ability to attach to existing processes, but turns out you don't need to attach... you can just create an attached browser directly out of the free version.

Epic win.

First, download the free version of Visual Web Developer 2008 here. Install it. Enjoy waiting twenty minutes. Get a cup of coffee. Don't sit there waiting for the worst out of box experience ever, whatever you do.

Next, go to Internet Explorer's Internet Options and set Internet Explorer as your default browser. I know, terrible, but you gotta do it -- otherwise VWD2008 tries to use Firefox, Chrome or your other superior default browser and you lose the ability to debug IE7 in all of its awful putrescence.

While you're in Internet Options, you should also de-select disabling script debugging and enable debug messages in the Advanced tab.

Now you have to create an Empty Web Project by clicking New > New Website. Now click Debug > Start Debugging. It'll open a new IE window pointed at localhost, but just fire up whatever to-be-debugged website in that window. 

Awesome. Now any errors should drop you into the VWD2008 debugger. ROCK ON.

FB Connect not working in IE? Fix your xd_receiver.html's HTML namespace extension

<html xmlns="" 

Internet Explorer 7 is very finicky with its processing of custom tags.

If you're using Facebooker, it actually currently does NOT include this in the html tag of the xd_receiver.html -- so if you try to log into fbconnect using IE7 on an app with the default generated file, it will just fail with a white screen in the login window.

TRICKY. But Forums and Google Search to the rescue once again.

I'm trying to blog these little stumbling blocks back because it'll help Google reinforce the right links just a bit more. Programmer solidarity =)

Running IE6, IE7 and IE8 on your Mac

I use a Mac, which means testing my work in IE6, IE7 and IE8 is a pain. I have Parallels installed but I don’t want to buy extra copies of Windows just to test in IE. Plus, Parallels doesn’t compress the virtual hard drive so each OS takes about 10 - 20GB of space.

The good news is that Microsoft provides free VirtualPC disk images for each of their browsers.

The bad news is that they wont run on Mac and VirtualPC wont run inside Parallels or VMWare Fusion — but I’ve found a solution! We can convert the disk images to work for VMWare Fusion or VirtualBox.

I'm giving this a shot... *crosses fingers* -- will update when it's good to go.