How Docker consume resource between containers

We recently started using Docker on our production servers and everything is working as it should. My questions is regarding container resources usage, I have a scenario like this, I have 5 domains running (with php-fpm image), each domain runs in its own container.

I have other containers, one running with nginx as a proxy server, other with MariaDB, and some other services containers.

I have set RAM, CPU and Storage usage on each container, ie each domain container to use 1Gb Ram, CPU and a specific storage, They all connect to the same host database server/container.

so in this scenario are domains containers also using database container resources (RAM/CPU/IO)?

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