While the word "scalability" refers generally to the ability to increase the size of any system in a linear manner without changing its fundamental properties, in the Internet environment and, more broadly in the world of networked computers, the word has come to refer to the ability to grow a network or Web site at the same rate at which use of the system is growing. Peter Loshin and his co-authors, writing in their book, Electronic Commerce, define scalability as follow: "The ability of a system with multiple available processors to call as many of those processors into service as necessary when system load increases, as well as the ability of that system to be expanded." Since all of the work on a Web site must be performed by central processing units (CPUs), the number of those processors and the manner in which they are linked is central to the concept. Loshin et al. link the concept to "performance," which they define, citing others, as "the ability to effectively increase throughput as needed on a single CPU in response to increased systems load." Performance is often an important aspect of adding users to a network.
Scalability became a central concern in the dot-com industry because popular Web sites can exhibit explosive growth. If they are poorly designed or difficult to scale up (because they slow down substantially as more nodes are added) demand is difficult to satisfy and traffic will decline.
While specialized software exists for those who want to attempt scalability projects on their own, many firms offer this service and help businesses design their sites to become efficient models of scalability. These firms are experts in the latest technological innovations and specialize in tiered Internet architecture that allows the site to grow without having to rewrite mainframe systems, while at the same time making better use of existing servers. They also help larger sites set up subdirectories within the domain directory to help serve a large number of accounts simultaneously. By performing these functions, scalability experts can help prevent Web site crashes and save the company lost revenue and damaged reputations.
The inability for an e-commerce site to scale properly could cripple their business. As Nicholas G. Carr stated in an article that appeared in The Standard: "On the Internet, if you can't scale—if you can't get really big really fast—you're nowhere. And it's not enough for just your technology to be scalable. Your entire business model has to have scalability, as well; you need to be able to quickly extend your business into new markets, either horizontally or vertically. 'Will it scale?' is one of the first questions venture capitalists ask."
While scalability is a critical issue for dot-coms, the actual advantage that comes with growing up to become a large Web site can still be debated. A larger site can appear to be more of a threat to a possible competitor that is thinking about entering the market, so much so that small sites are being bought up by larger sites in an effort cut down on the competition. This sort of consolidation can get pretty expensive, and presents a whole new set of scalability issues for the company that is doing the consolidating. Many dot-coms have learned the hard way about the problems that come with rapid and immense growth. A lot of the time, it is the consumer that gets hurt the most.
Carr sums it up by stating: "While scalability will continue to be critical for e-businesses, I doubt scale itself will provide much of an advantage. Companies will need to be able to expand their businesses fast, but their bigness won't ensure lasting success. Rather, once they've scaled up in one market, they'll need to immediately look for new markets in which to replicate their growth. Defense was the name of the game in the old economy. In the new one, offense is everything."
Carr, Nicholas G. "The Myth of Scalability." The Standard. 10 January 2000.
Killelea, Patrick. Web Performance Tuning. O'Reilly, 2002.
Loshin, Peter, John Vacca, and Paul Murphy. Electronic Commerce. Charles River Media, 2004.