CAP Theorem But Better? Introduce the PACELC Theorem
...In the previous blog, I introduced the famous CAP Theorem (please give it a read if you haven’t already before you start reading this one). It involves a trilemma of needing to give up one of the following three qualities: consistency, availability, and partition tolerance. Since all three are desirable features of modern-day distributed systems, determining which one to relinquish has become one of the most important and delicate decisions for designers of complicated distributed systems. While the CAP Theorem is widely-known in computer science, its extension, the PACELC theorem, has received less attention. Today, I will shine a long-overdue spotlight on the PACELC theorem.
What You Need to Know about the CAP Theorem
...The world that we live in is far from perfect. We constantly find ourselves in dilemmas, sometimes even trilemmas, that require us to make trade-offs. When shopping, we can only choose two out of “cheap,” “fast,” and “good.” In economics, a government cannot enjoy “sovereign monetary policy,” “fixed exchange rate,” and “free capital flow” at the same time. It can only achieve two of them by giving up the third. Similarly, the CAP (consistency, availability, and partition tolerance) theorem involves an equally head-scratching trilemma that has troubled computer scientists and software engineers ever since distributed computing became a popular solution to large-scale computation. Today, we will dive deep into the CAP theorem and learn how to make wise trade-offs based on our needs.