What is eventual consistency and when is it useful?
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Eventual Consistency is a consistency model used in distributed computing to achieve high availability. It guarantees that, given enough time, all updates to a system will propagate to all nodes, and all nodes will eventually agree on the same value. However, immediate consistency is not guaranteed.
When is Eventual Consistency Useful?
- High Availability Systems: Systems that require high availability and can tolerate temporary inconsistencies, such as social media platforms or e-commerce websites.
- Distributed Databases: Databases that are spread across multiple geographic locations where immediate consistency is challenging to achieve.
- Microservices Architecture: Systems where different services can operate independently and eventual consistency is acceptable for overall system stability.
- Scalable Systems: Systems that need to handle large volumes of data and require horizontal scaling.
Key Points
- Trade-off: There is a trade-off between consistency, availability, and partition tolerance (CAP theorem).
- Latency: Eventual consistency can lead to reduced latency in data operations.
- Conflict Resolution: Mechanisms are needed to handle conflicts that arise due to concurrent updates.
Example
A common example of eventual consistency is the Domain Name System (DNS), where updates to DNS records take time to propagate across all DNS servers globally.
