This should not require a ground-up rewrite though, unless the code is a big ball of mud in the first place. You might need to change the overall architecture (

This should not require a ground-up rewrite though, unless the code is a big ball of mud in the first place. You might need to change the overall architecture (e.g split monolithic code into to multiple services) and/or optimize some critical bottlenecks, but most code (business logic, UI etc.) will be unaffected.