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What is the path from PaaS to SaaS? Would it be a separate platform? For example, the company I work for has on-premises development and test environments and a separate production server with a "billing" or e-commerce interface with "production" or "golden" builds.
While you can transition from IaaS to PaaS or from PaaS to IaaS, there is no direct transition from either of these types of cloud platforms to SaaS.
Platform as a service (PaaS) is a system customers use to build a new application, while software as a service (SaaS) gives you an existing application run as a service. If you have your own in-house application, you need to either use infrastructure as a service (IaaS) or build the application for a PaaS cloud.
Some SaaS systems, however, offer a customizable platform. Software vendors such as Salesforce.com offer amenities that lend themselves more toward a traditional PaaS product than a SaaS cloud offering. In this example, you could have Salesforce.com configured for your e-commerce system and use their Force.com product (or any other PaaS system) to integrate with their application program interface for both your production and development code. You could also run two separate Salesforce.com environments to manage completely isolated development environments.
SaaS and PaaS: Building your own software on a vendor platform
If you're trying to build your own SaaS offering, using a PaaS to host and design your application is a huge bonus. It means you can create and deploy custom instances of your software for individual clients, and each of those environments can scale independently and automatically. You can quickly grow your business no matter how many customers you gain, while maintaining the performance levels your customers would expect. Make sure, however, to price your software appropriately according to what you'll be charged.
Say you're building an e-commerce SaaS, and you want to allow individual users to upload their own items with images, descriptions, prices and other metadata. You'll need to take into account not only how much data users will be uploading, but also how much usage they attract. A customer who only uploads a single item but processes 10 million transactions a day will cost your company a lot more than a customer who uploads 1,000 items but processes only five transactions a day. This can be a key problem with hosting on PaaS systems; you have to make sure your business model and pricing models fall in line with how you will be charged.
PaaS learning guide
What is PaaS? The growing role in 'as a service' family
Platform as a service: Advice for selecting a PaaS vendor
What you need to know about developing apps on SaaS platforms
Dig Deeper on PaaS and other cloud development platforms
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