Heroku

Heroku, which is now owned by Salesforce, was one of first PaaS solutions and it is still one of the best. While certainly not the cheapest solution out there, it is very fast to deploy applications to it, and it runs these applications very efficiently and reliably. It abstracts a lot of the complexities of building of web applications, making deploying one as simple as possible. At first, you could only run Ruby applications on it, but it now supports Java, Node.js, Python, Scala, PHP, Go and Clojure. It also has lots of database options, and other powerful features, and it all seamlessly scales as the application's user base grows. Heroku, though, can be expensive. Very expensive. It has a free tier, but it is very limited. In this tier, it will also put web applications to sleep if they receive no activity for 30 minutes. This means that if no one visits your site for a half an hour, the next person who does visit will have to wait as much as 20 seconds to get a response from the server. This makes the free tier usable only for testing purposes.