We have a monolith with 3 modules inside a one application
1 module is recieving a high demand
and we are scaling this monolith and creating a new instance of it

second choice we can separate this 1 module into a separate microservice and scale only it

and the question is, is the first scenario is more expensive in terms of resources
because if we scale one monolith, other modules are also scaled,
but I am wondering that modules in low demand not executed so much anyway so there should be no much resources allocted to it, so its better to do it one monolith app ?

I am expecting a solution combining less resource usage & less time to implement