Scalability Issues in Online Social Networks

The last decade witnessed a tremendous increase in popularity and usage of social network services, such as Facebook, Twitter, and YouTube. Moreover, advances in Web technologies coupled with social networks has enabled users to not only access, but also generate, content in many forms. The overwhelming amount of produced content and resulting network traffic gives rise to precarious scalability issues for social networks, such as handling a large number of users, infrastructure management, internal network traffic, content dissemination, and data storage. There are few surveys conducted to explore the different dimensions of social networks, such as security, privacy, and data acquisition. Most of the surveys focus on privacy or security-related issues and do not specifically address scalability challenges faced by social networks. In this survey, we provide a comprehensive study of social networks along with their significant characteristics and categorize social network architectures into three broad categories: (a) centralized, (b) decentralized, and (c) hybrid. We also highlight various scalability issues faced by social network architectures. Finally, a qualitative comparison of presented architectures is provided, which is based on various scalability metrics, such as availability, latency, interserver communication, cost of resources, and energy consumption, just to name a few.