The issue is not in 3%. Whole system should be designed with "performance in mind". It's architectural decisions, not just 3% of code, hidden in few fancy funct

The issue is not in 3%. Whole system should be designed with "performance in mind". It's architectural decisions, not just 3% of code, hidden in few fancy functions. Web app should be designed to insert caching layer or replace logging tool or error handling or email sending. When all is hardcoded into one huge monolith "it works", it will not be so important where are these slow 3%. And when each piece is optimized to be as performant as possible, only then whole app will be awesomely performant. It's not always necessary on the beginning, but to make it possible, each part should be replaceable to more performant and whole architecture should be designed "with performance in mind".