How well does WordPress scale?

Question

With the new Wordpress and it's new features, it seems like WordPress is capable of much more than a simple blog engine. But how well does wordpress scale being used by say 10k -> 100k users per day?

With that many users a big part of it will be to have a good cache strategy, but how well is WordPress developed to help, making this easy and give you the control you need. Fx being able to cache part of a page and only render user customized parts, support master/slave db setup and stuff like that?

Answer 1

Hi @googletorp:

Clearly nothing scales as well as static files served by a fast web server and any CMS that has to figure out what to load and then load it will not perform as well, WordPress or otherwise. One of the issues is the number of database queries required per URL request and my 2 prior years experience working exclusively with Drupal and now 2+ years with WordPress is that WordPress is much better in that department.

That said, almost nothing with any power is going to scale "out-of-the-box"; it's all about what can you do as your scalability needs grow?

On the low end of "lots of traffic" there are great caching plugins and integrations with inexpensive CDNs you can do a pretty good job on a no-IT budget and low hosting budget. Here are some other questions & answers to review:

• Steps to Optimize WordPress in Regard to Server Load?
• Options for CDN with WordPress Including Supporting Plugins?
• Configuring WordPress for Amazon CloudFront Caching?

There are options for profiling to identify performance bottlenecks:

• Profiling a WordPress Website for Deployment on Shared Hosting?

Once bottlenecks are identified you can do localized optimization with things like the Transients API. This Q&A gives an example that can be optimized using Transients API and shows how:

• Using WP_Query to Query Multiple Categories with Limited Posts Per Category?

If you thing really get want to pull out the big guns you can configure Memcached, HyperDB, Nginx and/or more to speed things up (it seems the latter is really evolving into the way to get amazing scalability out of WordPress):

• Enable Memcached for your WordPress
• How To Speed Up WordPress With Nginx And WP Super Cache
• HyperDB
• Nginx as a front-end proxy cache for WordPress

And finally there are emerging WordPress-focused webhosts specializing in performance such as WP Engine, ZippyKid and others:

• Best-of-Breed features of a high-end WordPress web host?

So the good news is all of the scales very nicely; from the very low end of free and easy with technical complexity and cost only grow as traffic significantly grows. Start small with WordPress and it will be great. If your traffic does grow and you are monetizing it even reasonably well you'll find it very cost effect to scale as you need it.

At least IMO. :)

Answer 2

1. Don't expect much from shared hosting--don't blame WordPress for slowness if you're on a shared host. Shared hosts might cram 1000s of accounts into one server. So you can spend all day optimizing a $10/month account and it won't matter. Also watch out for marketing buzzwords--just because it says "cloud" or "grid" doesn't mean you're not sharing a server with 100s or 1000s of people.

2. Personally, I don't think cache plugins are necessary at this point. If you look at the WP source code, there's already advanced caching baked into the core.

3. The only thing slowing you down (besides large media files) is slow MySQL queries, and WordPress out-of-the-box won't give you any trouble here. (Although I had to "LIMIT" my comments, is this fixed in WP 3.x?) If you're running into trouble with MySQL, it's probably a plugin that wasn't designed for high traffic.

4. I use a Linode 512 with NginX and "top" shows PHP and NginX doing their stuff in less than 1 hundredth of a second per request. Most of my CPU time and memory are tied up with MySQL. With this $20 account I'm sure I could serve 1 million pages per month without any issue. (Good month I serve ~333k pages.) If you look in the Linode forums, sounds like you can serve tons more than 1 million pages per month with just one Linode 512 before needing to upgrade to a Linode with more memory or moving MySQL to its own VPS (which would be super easy.)

5. In conclusion, WordPress itself is not really the bottleneck. At least in terms of money, your biggest expense is not servers--assuming your plugins aren't killing you. If you're running over 1 million visits/month, your biggest hosting expense is probably bandwidth, not the server!

Disclaimer: I don't work for Linode. The Linode 512, I believe you share it with 40 people. The bigger plans you're sharing with fewer people.

Answer 3

Very well.

http://wordpress.com

But you have to be diligent.