This depends on the circumstances.

• What is causing the troubles?
• Is it the amount of SQL’s?
• Or, are you CPU bound?

After you find the problem — which in web projects more often than not is the database — you can make an informed decision. And if you think another language/tech stack would solve this problem it is always better to rewrite ONLY the critical path and let the other stuff unchanged- of course this makes it necessary that you have an architecture where you can modularize if needed