One of the key system variables you have to deal with MySQL is innodb_buffer_pool_size, the size of the buffer pool, the memory area where InnoDB caches table and index data. You try to learn how to set a sensible value and you usually hope you do not need to change it too often.
One day you start to play with serverless databases and everything changes: you can see the value of innodb_buffer_pool_size changing real time, every few seconds. According to the load of your database cluster.
Next month I will dig deeper at Percona Live: looking at a direct correlation in the metrics between the capacity, the value of innodb_buffer_pool_size and the load of the database is just an interesting start.