Notes

The Principle at Scale

This principle works at all levels of scale. Mandelbrot got this so right. CPU cores are just nodes of execution and the cache system provides message passing for communication. The same patterns apply if the processing node is a server and the communication system is a local network. If a service, in SOA architecture parlance, is the only service that can write to its data store it can be made to scale and perform much better. Let’s say that underlying data is stored in a database and other services can go directly to that data, without sending a message to the service that owns the data, then the data is contended and requires the database to manage the contention and coherence of that data. This prevents the service from caching copies of the data for faster response to the clients and restricts how the data can be sharded. Encapsulation has just been broken at a more macro level when multiple different services write to the same data store.