The days of single-server apps have long been over; it’s now standard for a Web application to have multiple Web servers, one or more database servers, and a number of additional servers for other services, such as Redis, e-mail, and message queues.  VMs and containers (e.g., Docker) have made it easier to manage these individual servers, but how do you optimize the allocation, provisioning, and balancing of these servers? Mesos is an open-source project (sponsored by Apache) that manages clusters, and Marathon is a Mesos-based framework that handles scaling for large clusters. In this talk, Connor Doyle introduces Mesos and Marathon, and demonstrates how they can help growing sites to scale their server needs up and down, in an intelligent and controlled way.