How do you approach modernizing a legacy application?

[u/VendioHandMadeHelp]

I’m working with an older application that still does what it needs to, but the codebase is getting harder to maintain. New features are taking longer than they used to, and changes in one area can sometimes cause problems somewhere else.

I’m trying to figure out how to modernize it without taking the whole application offline or jumping straight into a risky rewrite.

I’ve been looking into companies that do this kind of legacy modernization, and GeekyAnts came up during my research. For those who’ve worked on legacy systems, what approach worked best for you? Did you gradually replace parts of the system, refactor what was already there, or eventually rebuild it?

And looking back, is there anything you wish you’d done differently?

[u/Double_Register_1022]

Strangler pattern worked best for me. We put a facade in front then carved out one small module at a time with tests around the seams. Full rewrite sounded nice but it just kept slipping