How do I use WordPress for high traffic sites?

To get things started, you will either need WordPress hosting or run your own VPS or dedicated server. My recommendation would be to use NGINX server, it's much more performance oriented. WordPress.com runs on NGINX. Unless you have a huge budget to maintain custom WordPress core, don't even think about touching it. It's a well designed and developed machine. It just needs a good driver, mechanic and the a good road. Next, you need to keep your plugins down to a minimum. It's hard to do when you want to add this feature or that feature, but these decisions should come from user testing, analytics, and user feedback. Otherwise your assumptions will only bloat your WordPress, and in worse case, turn visitors away. You might want to consider using third-party related posts service, rather than something that uses your database and resources. Most related posts plugins are very resource and database intensive, and will slow your site down. You should stay away from themes that have "drag and drop" features, or are designed for non-technical users. Ease of use comes with the price of having too many files, too much code, and a bloated theme. I'm not saying they are not well developed, I'm just saying they can put a drag on your performance when your visitor count goes up, up, up. Next, caching. Don't even think picking anything but W3TC caching plugin. You'll need to tune it for your server/hosting, and ideally you'll have server side caching like APC, maybe Varnish. I would also highly recommend adding CDN service to speed up performance. I would recommend MAXCDN, we use it and it's affordable. But, you can and should go with Cloudflare for added performance boosts. One of my sites uses both MAXCDN and Cloudflare. I like Cloudflare for their added performance features and security layer. With CDN, especially Cloudflare, you will also be able to decrease resource usage on your server, like bandwidth. If you don't use Cloudflare, do consider at least Google's Pagespeed mod for your server to run some optimization to improve performance. That's my 2 cents.

The Wordpress Codex has some useful info on this very topic: http://codex.wordpress.org/High_Traffic_Tips_For_WordPress PHP is very fast. MySQL is going to be the weak link in the chain. So, if you're scaling up for heavy traffic, you're probably going to want a hosting plan that can adapt to database usage spikes.

Disclaimer: My experience with 'high traffic' sites is limited to several thousand unique visitors a day. WordPress core is pretty well optimized for high traffic, so apart from the usual caching and CDN solutions and server side tricks there is not much to be done. WordPress has plugins both for caching and CDN, and they do the job well (did for me, at least). Just make sure to not overcrowd the site with plugins, and your theme should try to avoid making too many queries to the database, if possible. http://codex.wordpress.org/Transients_API should be your friend. The only real problem I encountered was not really traffic, but rather content related. Big sites tend to accumulate a lot of data - posts, pages, images, attachments, custom posts, etc. And all of that in WordPress database structure gets stored in a single table - wp_posts. When this table reaches 10k-12k entries, the infamous SQL_CALC_FOUND_ROWS issue kicks in, making frontpage load really slow (I am talking seconds). This is solved by not using WordPress default option on Settings>Reading>Front page displays : Your latest posts. If you switch that to "Static page" and then build custom loop with 'nofoundrows'⇒true'no_found_rows' => true set for front-page.php, that issue goes away. Disabling or limiting the amount of post revisions also helps to make the database smaller.

and made it pretty clear. CDN & VPS are going to be your best friend in maintaining any high-traffic website and W3TC or https://wordpress.org/plugins/wp-super-cache/ is especially for Wordpress. Always avoid unnecessary plugins that create cron jobs which would eventually increase the server load so always be specific about the plugins that you are going to use. But with VPS and CDN you can run a very high traffic site decently and if it still doesn't help you, then a dedicated server could solve the issue.

I use static caching and Disqus. It's the PHP that kills servers, and using something like "really-static" that converts the site into flat HTML solves that problem, especially if you offload the commenting system to someone like Disqus or Facebook to manage the comments, loaded inline with JavaScript. Oh, and putting Cloudflare in front of it helps, too.

I am not a specialist in this field, but I know there are set-ups that are specifically available for high-performance Wordpress installations. There is also a plugin available that performs improved caching which helps a lot. And indeed, a theme that doesn't add too much 'extra' to a website will do a lot as well.

i think your problem is already solved... by long term vision, there's no need making any change to wordpress core as it can handle most high traffic site. though you may need to install more plugins and modules as time goes on to solve other problems that may present themselves... if your hosting environment is up to the task, wordpress will definitely perform well regardless of the traffic....

The site that we created this case study on is a wordpress site:http://www.ranky.co/how-we-made-logdogs-traffic-explode-by-700-using-inbound-marketing-seo/ hope this helps :)

While I have no doubt that Viktor's answer is technically correct, I wonder if it is the right approach.  You sound like you are a pre-revenue startup.  And, depending on your funding situation... you might want to think in phases.  Planning and building for scale before you know whether you need scale may not be the right approach.  One way to approach this is to use a simple drag-n-drop WordPress builder... throw the site up and start marketing.  You are bound to learn a ton about what is working, not working.  Once you get the site structure / marketing approach nailed and you see scale, then hire someone to build you a custom WP site that scales well.  I have been down the road of building for scale before having it and I can tell you it can be expensive and slow. Just my two cents.