We're not exactly a startup, but a small growing data science, analyst, and engineering team in a bigger company. You name it... but a typical data and web stack.

OS/Distros: FreeBSD and Linux (CoreOS and CentOS)

Languages: Python (Data Science) & Javascript (Front End)

Frameworks: Flask, Django, Angular, React, Bokeh, Tensorflow, Scikit-learn

Container Services: Docker, Mesos/Marathon/DCOS (currently testing Kubernetes in GKE - Google Cloud)

Databases: Redshift, Postgres, Cassandra/Scylla

Deployment Tools: Jenkins, Github, Gitlab (different team)

All running in AWS deployed through CloudFormation and Salt.

There's even a Windows Server 2016 instance thrown in there for good measure running Tableau. That's the most reliable part of our stack. </rolls-eyes>