Real-time applications, such as disaster early warning systems, live event broadcasting, video conferencing and online gaming, present particular challenges for successful development and deployment: they only achieve their expected business value when they meet critical requirements, such as high performance and availability for outstanding Quality of Service and Quality of Experience. The development of time-critical applications needs to be supported by a customized software engineering environment that offers support for the entire application life-cycle. However, there is a lack of (component-based) software workbenches/tools suitable for time-critical applications, supporting customized software engineering through the entire life-cycle. In this paper we present the SIDE Workbench developed during the course of the SWITCH project. It uses TOSCA extensively for exchange of information within the SWITCH platform, and offers component-based application composition, software component modelling, infrastructure planning and provisioning through the entire life-cycle of time-critical applications. To show the application composition process we describe the development of a containerized interactive multi-tier application on the SIDE Workbench that is mapped into TOSCA, from which the corresponding Docker Compose file is then created.