This strategy works especially well if your product provides an API and your customers or partners are motivated to work with you. Then, besides your suite of t

This strategy works especially well if your product provides an API and your customers or partners are motivated to work with you. Then, besides your suite of tests, you can use the customers’ products as verification. That is, if the customers products still work, then you can be confident that your rewrite works. I’ve done this several times with success. There was a period of about 10 years where I specialized in rewriting legacy code. The first case, I rewrote 200k lines of C++ (COM/OLE) code in Java. Then, I joined a startup that had to scrap its entire codebase because of scaling issues. Then, I worked for two other companies that had acquired other software companies (with crappy code), and I led the rewrite and integration efforts. These are the notable ones. Believe me, rewrites can be successful. They must be done carefully. But, there are lots of ways to manage the process and mitigate risks. I’ve done it at least 10 times, and I’ve never had a failure or substantial cost or schedule overrun.