Stateful: you have one web server!<p>Stateless: you grow to require tens of servers or more, horizontal scalability is much cheaper than vertical, look to software solutions to help slow expenses, move to NoSQL clustered DBs like Riak, Casandra, Hadoop, etc. 1-2 engineers can still run the whole show, cloud services, SaaS and PaaS are employed.<p>Stateful: you run thousands of servers, having since brought many services back in-house. Many if not most are your own metal, with dedicated staff. Looking to slow power bills and space requirements, you look once again at software solutions.<p>If you stay at the same growing company long enough, what&#x27;s old will be new again.