Lessons learned migrating complex software
summary
A yearlong incremental migration moves Songkick from Angular 1 to React using the strangler pattern and ngReact to render React inside Angular templates, shipping the first migrated listing date in a day. Unit tests move from Karma to Jest, acceptance tests run with Protractor and Selenium, and the queue is rebuilt over two to three weeks. Prioritization uses churn and bug frequency, a repo markdown knowledge base captures gotchas, daily small deploys minimize risk, and long‑running bugs in payments and queues get fixed.
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chapters (15)
- 0:00Intro
- 0:35Migrating complex software @Jack_Franklin
- 6:41We shipped migrated code the day after starting this migration.
- 10:30Unit tests are coupled to the implementation code.
- 10:47Acceptance tests Automated tests that are entirely decoupled to the application code.
- 13:20Pick work based on bugs and churn rate, not code quality
- 17:29A migrated codebase is not a perfect code base
- 22:05Migrations are a good excuse to upgrade your tools.
- 22:40The most important people to convince are not in your tech team.
- 23:12And they don't care about frameworks
- 24:29Fix bugs that cause pain for other departments
- 27:15Takeaways
- 27:39Cross business communication is so important.
- 27:49Prioritise based on pain points in your current application
- 28:01Have metrics to track progress internally and externally
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