Singularity is an open source, battle-tested framework for Mesos Clusters. It combines distributed job scheduling and lifecycle automation of resilient microservices. It is ideal for building PaaS infrastructures that can help high growth companies to sustain development velocity by significantly reducing the operational complexity and deployment friction. In this presentation, we share our experiences in developing the HubSpot PaaS / Deploy pipeline and in moving all our QA and production environment to Mesos. Our key goals are: a) to demonstrate that Mesos clusters provide a mature, safe and proven solution for deploying highly available, complex software architectures comprised of thousands of components, b) to prove that Mesos clusters are not only for the big boys and invite medium size companies to follow HubSpot example and start reaping the benefits of Mesos.