Orchestration, Code, Deployment, Infrastructure
Managing code is a solved problem. Git plus Github are everything we need and more. Docker and LXC containers, plus Ansible, Puppet, Chef, on IaaS like AWS, Google Cloud, and Azure provide previously unimaginable possibles for deploying services onto consistent infrastructure. Yet no web application is really whole without data, and, in fact the code, data, and infrastructure all need to fit together in exactly the right way, or you don't have an application, you have an unholy mess.
Platform.sh solves the problem of starting every branch of your development on a fully orchestrated environment that has a consist copy of the code, data, and infrastructure of the live application. In other words, you develop directly on a clone of the app. Think about this problem: the metadata for uploaded files is stored in your database; if you synchronize your database from a live application to a development environment, but not your files, you have an inconsistent application. Same with a Solr or Elasticsearch index.
Without the four components of orchestration, code, infrastructure, and data, web application development is non-deterministic, and therefore risky. The big challenge is setting up and infrastructure that extends these guarantees to each developer on your team, for each branch of development that they're working on. That's the promise of Platform.sh.
Platform.sh is optimized for Drupal and Symfony