For instance, change the memory limit
memory_limit = 2G #Default is 1G
You can just restart the FPM container, if it is already running. This will reinitialize the configuration with your changes.
docker-compose restart fpm
docker-compose run deploy bash
Inside the container run the following command
php -i | grep "memory_limit"
Results will look like the following.
root@deploy:/app# php -i | grep "memory_limit"
memory_limit => 2G => 2G