IoT developers need to integrate a variety of protocols, backend components and services; they often need to pre and post-process data as well as react to changes in the real world. Data flow

programming tools have been introduced in a number of related domains to provide a flexible, but easy to use visual programming environment for rapid development. The open source Node-RED system provides such a tool for IoT applications, but is limited to executing a single flow file in a single thread. In this paper we describe the design of our system called the Front-End for Node-RED (FRED) that manages multiple instances of Node-RED for logged in users, allowing Node-RED to be used as a cloud-hosted data flow mashup tool for the IoT. We present some examples of how some of our 1800+ users are using FRED for IoT mashups, and some of the challenged we faced in implementing the FRED system.