Have you ever studied or worked with databases, come across abbreviations such as ACID, BASE, and CAP, and wondered what they mean? I have, and this post is the result of my research into them.

Is CAP a type of headwear?

CAP stands for Consistency, Availability, Partition-tolerance. Eric Brewer introduced it in a talk in 2000. He argued that when a partition disrupts network communication between nodes in a distributed system, the system must choose between consistency and availability. It cannot guarantee both. What are these properties, and why can we not have both?

When working on backend systems, we often follow a common pattern for handling incoming data. A server receives data from a message broker or an API, processes it according to the business rules, and inserts or updates it in the database. It then sends the processed data to the next server through a message broker or an API. This pattern is called dual write, sometimes also called multi-write or sync-write.