## 1 Introduction  
Even tiny companies can generate enormous economic growth and business value by providing cloud-based services or applications--Instagram, Uber, WhatsApp, NetFlix, and Twitter--and many astonishing small companies (if we relate the modest headcount of these companies in their founding days to their noteworthy economical impact) whose services are frequently used. However,even a fast-growing start-up business model should have its long-term consequences and dependencies in mind. A lot of these companies rely on public cloud infrastructures--currently often provided by Amazon Web Services (AWS). However, will AWS still be the leading and dominating cloud service provider in 20 years? IT history is full of examples of large and well-known companies failing and (almost) dieing: Atari, America Online (AOL), Compaq, Hewlett Packard, Palm, and Yahoo. Even Microsoft--still a prospering company--is no longer _the_ dominating software company that it used to be in the 1990s and 2000s. Microsoft is even a good example of a company that has evolved and transformed into a cloud service provider. This might be because cloud providers are becoming more and more critical for national economies. Cloud providers run a significant amount of mission-critical business software for companies that no longer operate their own data-centers. Moreover, it is very often economically reasonable if workloads have a high peak-to-average ratio [1]. Thus, cloud providers might become (or even are) a too-big-to-fail company category that seems to become equally important for national economies like banks, financial institutions, electricity suppliers, public transport systems. Although essential for national economies, these financial, energy, or transport providers provide just replaceable goods or services--commodities. However, the cloud computing domain is still different here. Although cloud services could be standardized commodities, they are mostly not. Once a cloud-hosted application or service is deployed to a specific cloud infrastructure, it is often inherently bound to that infrastructure due to non-obvious technological bindings. A transfer to another cloud infrastructure is very often a time-consuming and expensive one-time exercise. A good real-world example here is Instagram. After being bought by Facebook, it took over a year for the Instagram engineering team to find and establish a solution for the transfer of all its services from AWS to Facebook data centers. Although no downtimes were planned, noteworthy outages occurred during that period. The NIST definition of cloud computing defines three basic and well-accepted service categories [2]: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Sevice (SaaS). IaaS provides maximum flexibility for arbitrary consumer-created software but hides almost no operation complexity of the application (just of the infrastructure). SaaS on the opposite hides operation complexity almost entirely but is too limited for many use cases involving consumer-created software. PaaS is somehow a compromise enabling the operation of consumer-created software with a convenient operation complexity but at the cost of following resource efficient application architectures and accepting to some degree lock-in situations resulting from the platform. Throughout a project called CloudTRANSIT, we searched intensively for solutions to overcome this \"cloud lock-in\"--to make cloud computing an actual commodity. We developed and evaluated a cloud application transferability concept that has prototype status but already works for approximately 70% of the current cloud market, and that can be extended for the rest of the market share [3]. However, what is essential: we learned some core insights from our action research with practitioners:  
1. Practitioners prefer to transfer platforms (and not applications). 2. Practitioners want to have the choice between platforms. 3.