In this paper, the CALM Theorem is introduced as a solution to the issue of when coordination is necessary in distributed systems. CALM, which stands for “consistency as logical monotonicity”, reveals that programs with consistent, coordination-free implementations can be expressed in monotonic logic. This has practical implications for developers, offering a new perspective beyond traditional storage consistency. The CALM Theorem challenges conventional wisdom in system design, including the CAP Theorem, and suggests that adopting a monotonic mindset can influence the development of distributed systems. Additionally, new programming languages and tools are discussed as aids for creating consistent, coordination-free code.
https://arxiv.org/abs/1901.01930