When trying to build a highly scalable system the single biggest limitation on scalability is having multiple writers contend for any item of data or resource. Sure, algorithms can be bad, but let’s assume they have a reasonable Big O notation so we’ll focus on the scalability limitations of the systems design.
I keep seeing people just accept having multiple writers as the norm. There is a lot of research in computer science for managing this contention that boils down to 2 basic approaches. One is to provide mutual exclusion to the contended resource while the mutation takes place; the other is to take an optimistic strategy and swap in the changes if the underlying resource has not changed while you created the new copy.
The Single Writer Principle is that for any item of data, or resource, that item of data should be owned by a single execution context for all mutations.
Original title and link: The Single Writer Principle ( ©myNoSQL)