.NET Architecture & System Design Interview Question #72

What is eventual consistency?

Database Scaling, Partitioning, NoSQL & Data Consistency Mid-Level Intermediate

Quick Interview Answer

Eventual consistency allows replicas or derived views to be temporarily different after an update, with the expectation that they converge when updates stop and communication succeeds.

Detailed Explanation

Eventual consistency allows replicas or derived views to be temporarily different after an update, with the expectation that they converge when updates stop and communication succeeds.

It is appropriate when temporary staleness is acceptable, such as analytics, search indexes, or some asynchronous integrations. Business rules must explicitly account for the period in which different components see different states.

Code Example

Primary: X = 10
Replica: X = 9
    |
replication
    v
Replica: X = 10 eventually