Not to long ago we where approached by a new client. They where an online auction company and had written software using PHP and MySQL. Fortunately for them, their company was taking off in Australia. Unfortunately for them their application wasn't well written and didn't scale to meet their client load.
The simple short term solution was to through more hardware at the problem. Overnight we migrated their application to the cloud and distributed the system from one server to seven servers. This solved the scalability problem.
Over time we worked with the client to make incremental improvements in the software so that they could support a larger client base with reduced hardware overhead.