Say you’re developing and testing an application in the cloud  using a public PaaS. However, all your databases reside in  your on-premises data center. That can get complicated. Or,  say you’re building an application using a private PaaS, which  needs to access your CRM system that is in the cloud. There needs to be a way for the two environments to share  information. The question becomes, how do you manage  workloads across potentially incompatible environments? Application programming interfaces  (APIs) allow communication  to occur between products and/or services. For example, if  you’ve developed a gaming application you can write an API  that allows other developers to write to your application. The  API specifies how one application can work together with  another one. It provides the rules and the interfaces. The  developer doesn’t need to know the nitty-gritty of your application because the API abstracts the way these programs  can work together. APIs are important for managing workloads in a cloud environment. For example, APIs allow a developer to build an  application that runs on top of a public IaaS service. In fact,  every company that offers foundational cloud services, such  as IaaS, PaaS, and SaaS, provides APIs for its customers. The sticky point with APIs and the cloud is that different  APIs aren’t always compatible. For example, you may build  an application on top of an IaaS offered by one vendor, but if  you want to move it to another cloud provider, it may require  extensive re-programming. No standard API exists that enables the developer to work in  different cloud models provided by different cloud vendors.  What is actually needed is a standard layer that creates compatibility among cloud workloads. Of course, you can  always find ways to work around complicated problems. A standard workload layer  Chapter 4: Managing Cloud Workloads and Services 41 The importance of APIs These materials are the copyright of John Wiley & Sons, Inc. and any  dissemination, distribution, or unauthorized use is strictly prohibited.