A hackathon (hacking marathon) is an event to innovate and develop prototypes, typically lasting at most a few days. Despite several innovations having been reported resulting from hackathons and the increasing popularity of hackathons, results about, organizing of, and experiences regarding hackathons have been scarcely reported. We studied a hackathon as a means to assess a device-centric cloud ecosystem in industrial settings. We provide a descriptive account of a three-days hackathon. The experience was that the hackathon was realistic as well as an efficient and effective assessment of the requirements and design of the ecosystem, providing guidance for future development. We also summarize the lessons learned about successfully organizing a hackathon. The results also highlight encouraging experience about the hackathon among the participants in terms of the social benefits, such as collaboration, inspiration, and work motivation, resulting in repeating hackathons for various purposes in the near future. In general, the results indicate a hackathon as a promising new approach in software engineering, where speed of development is becoming essential.