Date: 2025-06-18
Proposed
Development of the Mavis application thus far has been in Ruby on Rails, as detailed in ADR 00004. This was deemed acceptable at the time, as Ruby was on the Tech Radar as PROPOSED and initially the project was viewed as a Proof-of-Concept.
However, now that Mavis has progressed to processing real-world data from genuine clinical practitioners, we have been advised that new components must be developed in a MAINSTREAM technology. We are about to start on a moderately significant piece of work to meet the reporting needs of the NHS Commissioners and the SAIS teams which report data to them, and this work is sufficiently self-contained that it lends itself to being used as a pilot for a mainstream technology.
We have decided to adopt Python as the MAINSTREAM technology. (see entry in the Tech Radar)
Justification:
- other teams in NHS Digital are already using Python for similar web-based services, providing the opportunity for reuse and sharing of common components such as NHS Design System implementation
- similar paradigm to Ruby - a general-purpose procedural language with functions and classes, suitable for scripting and back-end data processing as well as web development
- there are web frameworks available for Python which are similar in approach to familiar Ruby frameworks (Django approximates Rails in functionality, Flask is more similar to Sinatra)
- several of the existing team are already somewhat familiar with Python
We will need to create a new repository for the Python application, and configure CI/CD pipelines appropriately for a different build pipeline. Future ADRs will consider:
- the appropriate AWS architecture changes to allow Mavis to serve & monitor two separate application processes behind a single user-facing domain
- authentication mechanisms such that the user will only have to log in once to both applications, whichever they visited first