I'm planning on adding Redis support soon enough so that sudden spikes would have little impact on the database server (which is nearly always the bottleneck, unless you're compute-intensive, which isn't the case with Commento). So that if you suddenly get a few hundred thousand visitors, most API responses are cached and only a fraction will actually require disk access. Like reddit does, where it'll temporarily say there N comments, but when you open the page, there wouldn't be that many. A few seconds of inconsistency is a fine compromise in the comments world. Of course, Redis isn't going to magically make everything faster, so I'll have to be careful with where I introduce it. Optimise for the common case and all that.

I'm still in uni, and I've never actually worked on large-throughput, high-scalability stuff before, so all this has been a great learning experience for me. If you have any suggestions or war stories that might be relevant, I'm all ears!