I did this once as one of my first big projects. I was tasked with re-implementing a system that had been written in FORTRAN and some legacy databases and bring

I did this once as one of my first big projects. I was tasked with re-implementing a system that had been written in FORTRAN and some legacy databases and bringing it up to date (to C++ and a SQL database). There were also a couple extra features that they wanted. It took me about 2 years. I ended up leaving for another job as I was getting started migrating stuff into the new system. Someone else ended up taking over and finishing the job. I should probably mention I went the rewrite route. I hadn't even considered the option to port it, I think I would have rejected it as infeasible due to my juniorness, and to be fair given my juniorness I don't think I had the skills or know-how to port such a thing. But at the end of the day it led me to realize that porting it probably would have been easier and less of a pain. When you rewrite, you have to re-invent every little detail. Every little hack, every little or big workaround that the original system wasn't flexible enough to handle (or the original programmer didn't have time to do correctly). The bigger the system, the more these details pile up and keep. getting. in. the. way. of. finishing. At the end of the day it wasn't that satisfying. I modernized something that needed occasional maintenance, and I didn't really improve performance that much, not in any way that mattered to the bottom line. The project did a good job of giving me experience with programming, and then I took that experience and went elsewhere lol. But that's on management and overall I think they were happy with my efforts. You're right to approach it with due caution. Best of luck!