Thanks to discussions around a post for a company blog I came across the paper “An Agile Approach to a Legacy System”. It’s been published 11 years ago, but I’m surprised how relevant it is today. It reads like a novel, so I really recommend to give it a go.

A few things that really resonated with me:

– Legacy code is not (only) a technical problem. The authors mention that trust and politics are important factors. Like it or not, you can’t go away without it and very often “human factors” determine whether you succeed or not.

– If you want to build something better than the legacy system then you need to focus on the users. Find their current pains and solve their problems, provide business value. If you do your job well they’ll become the biggest advocates of your work.

– Take care of yourself and your team. Take breaks, don’t overwork yourself. Take time to bond. Take pride in your work. Work on interesting problems and have fun!

– If you rewrite legacy code you’ll reproduce legacy system. Since I’ve worked on a few systems that have been rewrites of the legacy I know what they’re talking about here 😉 You can throw in new shiny technologies and come up with better architecture diagrams but it still doesn’t feel quite right.

There is also a list of “case-studies” for projects where this approach was used.