Chandrasekaran, K.Marimuthu, C.2026-02-082016Encyclopedia of Cloud Computing, 2016, Vol., , p. 150-16297811188219309781118821978https://doi.org/10.1016/j.ecolmodel.2025.111162https://idr.nitk.ac.in/handle/123456789/33971Software as a service (SaaS) is emerging as a widely used software delivery model, which is receiving a lot of attention across industry and academia. It is not only a software delivery model; it is also a business model that allows the SaaS provider to make money and SaaS consumer to save money. It gives rise to a lot of challenges and research opportunities in SaaS development, which will be discussed in this chapter. The chapter begins with basic understanding of cloud computing and SaaS followed by a discussion of the challenges and research opportunities to address them when developing SaaS. Then it covers the popular SaaS development platforms available for public cloud and private cloud followed by multitenancy at database level to secure the user data on cloud platforms. Finally, this chapter presents the best practices to transform traditional Web applications to cloud-based multitenant SaaS applications. © 2016 John Wiley & Sons, Ltd.cloud computingcloud software developmentmultitenancyPaaSSaaS