> The way it usually works, if 1 of your 100 modules needs to be scaled, it probably means the overall monolith only needs a small amount of extra resources, since that module is only using 1% of the total. So it's not like you need to double the instances of the whole thing.
I could be wrong but doesn't monolith usually refer to one really heavy app? As soon as you go from needing 1 instance to 2 (because 1 of the 100 inner "modules" needs to be scaled), I would guess most of the time there's a high expense (lots of memory) in duplicating the entire monolith? Unless you can scale threads or something instead of the entire process... Or if the entire process doesn't initiate 100 modules as soon as it is started (although I imagine it would in most cases)
>doesn't monolith usually refer to one really heavy app?
No. Backend Server clusters are around almost as long as the internet exists.
>I would guess most of the time there's a high expense (lots of memory) in duplicating the entire monolith?
That's right, but there's a gotcha. Everytime you split your monolith into parts, that doesn't mean that each part will consume 1/n of original monolith startup resource. There will be a floor of memory usage.
Consider 1 monolith that eats up 1GB to startup vs 4 microservices that uses 512MB each. Right from start you doubled the wasted memory from 1GB to 2GB. That only gets worse the more services are created.
Another problem is that microservice/cloud folks loves to create anemic machines. Usually setting up 512MB RAM and half a core cpu to a service that needs 380mb minimum :) Thats 75% overhead and 25% of working memory. It's bonkers.
You do lose some memory to holding unnecessary code and whatever data caching that a module does. But it's not generally very much and large data caching can be pushed to Redis. If you're not buying your servers by the rack or data center it's ultimately negligible compared to development cost.
I could be wrong but doesn't monolith usually refer to one really heavy app? As soon as you go from needing 1 instance to 2 (because 1 of the 100 inner "modules" needs to be scaled), I would guess most of the time there's a high expense (lots of memory) in duplicating the entire monolith? Unless you can scale threads or something instead of the entire process... Or if the entire process doesn't initiate 100 modules as soon as it is started (although I imagine it would in most cases)