> I'm curious about real world examples where a change has lead to a significant positive outcome in performance, code quality/maintainability, etc.
I wanted to build a database in a dynamic language. While others have succeed to do so by layering their DB on top RDBMS (like EdgeDB or Datomic) I went lower level and built a datomic like DB with GNU Guile Scheme using wiredtiger (now mongodb storage engine). The reason for that is that Guile doesn't have a Global Interpreter Lock (GIL). Using the same design in Python would simply not be possible. I did not benchmark, but I don't think it's possible for a single thread DB to be faster than multithread DB. In this chance changing language made the project possible.
I wanted to build a database in a dynamic language. While others have succeed to do so by layering their DB on top RDBMS (like EdgeDB or Datomic) I went lower level and built a datomic like DB with GNU Guile Scheme using wiredtiger (now mongodb storage engine). The reason for that is that Guile doesn't have a Global Interpreter Lock (GIL). Using the same design in Python would simply not be possible. I did not benchmark, but I don't think it's possible for a single thread DB to be faster than multithread DB. In this chance changing language made the project possible.