  Data analysis in HEP has often relied on batch systems and event loops; users
are given a non-interactive interface to computing resources and consider data
event-by-event. The "Coffea-casa" prototype analysis facility is an effort to
provide users with alternate mechanisms to access computing resources and
enable new programming paradigms. Instead of the command-line interface and
asynchronous batch access, a notebook-based web interface and interactive
computing is provided. Instead of writing event loops, the column-based Coffea
library is used. In this paper, we describe the architectural components of the
facility, the services offered to end-users, and how it integrates into a
larger ecosystem for data access and authentication.
