My team’s greatest achievement was upgrading our old codebase from Python 2.7 to 3.6 and Django 1.5 to 3.0. This required upgrading packages, rewriting a lot of code, extensive testing, and QA.  Once our codebase was improved, we then set out to improve our staging, prod test, and production environments by creating automatic deployments on Bitbucket using Docker on our servers. The overall project was a success and took about 6 months to complete while maintaining the original site.