Martin Fowler’s website is a cornucopia of patterns that are conducive to gradually improving the architecture of large, sprawling codebases. Take the strangle

Martin Fowler’s website is a cornucopia of patterns that are conducive to gradually improving the architecture of large, sprawling codebases. Take the strangler pattern, for instance: https://www.martinfowler.com/bliki/StranglerApplication.html https://www.martinfowler.com/bliki/StranglerApplication.html Any useful suggestions necessarily will have to remain at a pretty high altitude, though, simply because no two large applications are completely alike. Other than that there are a few general principles and guidelines you might want to follow: - the Boy Scout Rule: When you’re working on a particular piece of code and you see something weird or overly complex try to clean up the code. Start small while doing so. Don’t try to refactor everything at once. - Before refactoring or otherwise introducing significant changes try to write unit tests that ensure the previous, expected behaviour still is present when you’re done with your refactoring. - Having inherited a Java codebase (i.e. one written in a strongly rather than weakly typed language) probably will prove to be a boon further down the line. If you break something many errors will show up immediately during compilation and not just once the application is in production. - This allows you to refactor relentlessly and make full use of the refactoring features of an advanced IDE such as IntelliJ IDEA. Speaking of tools: You’ll want the best tools available to help you with this daunting task, i.e. - state-of-the-art CI / CD - IntelliJ IDEA Ultimate licences for every developer (or whichever IDE you prefer, just don’t try to be cheap at the expense of productivity) - an automated code quality checking and code exploration tool such as SonarQube.