Data Consistency Models

In distributed systems, data is often copied and stored on multiple servers. Data consistency refers to ensuring that all these copies of data are the same at any given time.

Think of it like having multiple copies of a book. If you update one copy, how quickly and reliably do all other copies get that same update?

The CAP Theorem is a fundamental concept in distributed systems. It states that a distributed data store can only guarantee two out of three properties at any given time:

• Consistency (all nodes see the same data at the same time)
• Availability (every request receives a response, without guarantee of it being the latest write)
• Partition Tolerance (the system continues to operate despite network failures)

When designing systems, we often make trade-offs, especially between Consistency and Availability.