Forrester's report emphasizes that PaaS remains "an immature market with lots of potential risks for buyers," says analyst Ried. But he also believes IaaS ultimately offers less value: "You just get the virtualized hardware." Developers using IaaS offerings such as Amazon Elastic Compute Cloud (EC2) must deal with virtual machines, storage blocks, execution threads, and network connections.
WebFilings does maintain 10 percent of its operation on the Amazon EC2 IaaS platform for some CPU-intensive processing, but if WebFilings had been launched formed today, Murray says Amazon EC2 probably would not be needed at all, thanks to App Engine's subsequent improvements.
Developers to drive the growth of PaaS -- individuals first, enterprises later
PaaS growth will be driven in part by the frustration of application developers who do not want to invest much effort into putting together middleware components, Ried says. "Cloud computing is exciting for application development and delivery pros because it offers instant access to resources for development and testing; deployment in minutes; easy, even automatic scaling up and down; and pay-for-what-you-use pricing," he wrote in his report.
Today, the vast majority of PaaS users are individual developers turning to the cloud to build relatively simple applications, says Massimo Pezzini, a Gartner analyst. But enterprise adoption is growing at least for development and testing purposes, if not necessarily for deployment. The reason: Barriers still exist such as security, data confidentiality, and concerns over quality of service. "With a product like App Engine, you don't really have any QoS [quality of service] assurance," Pezzini says.
Programming languages abound
Developers seeking a PaaS offering can probably find one that accommodates the programming language of their choice.
The variety exists because no dominant PaaS language has yet emerged, Pezzini says: "At the moment, a Darwinian survival of the fittest [battle] is going on as far as programming languages for PaaS." Languages such as Java will likely be among the survivors, he says, as well as dynamic languages like Ruby: "However, brand-new languages, specifically designed to take advantage of multicore capabilities and cloud parallelism, like Scala, and model-driven environments, like BPMN, will also play an important role."
Integration PaaS is emerging
Another variant of PaaS, integration PaaS (iPaaS) -- or more simply integration as a service -- is becoming important for connecting cloud applications with one another or to on-premise applications, Pezzini says. (He uses the term "application PaaS," or aPaaS, to refer to "traditional" PaaS.) He estimates there are between 2,500 and 3,000 organizations using integration PaaS.
Clouds such as Azure and the newly introduced MuleSoft Mule Ion offer integration PaaS. "The new problem that's emerging is we're creating cloud silos," says Ross Mason, MuleSoft's CTO, which the integration services are meant to connect.