From a post on reddit websites a person running reddits web servers said they moved the reddit website to the cloud hosting and reddit runs on virtual servers.
According to the post on reddit. Reddit is hosted on 218 Virtual CPUs running 380GB of RAM to host all the content and serve the webpages to it's users.
As of now the other specs of the virtual servers that reddit is hosted on are.
9TB of Block Storage
2TB of S3 Storage
6.5 TB of Data Out / mo
2TB of Data In / mo
156M+ Pageviews
Cloud hosting is really the way to go for hosting any website and especially large websites as it's very easy to scale the hosting environment as your website traffic increases.