Basically Available, Soft State, Eventual Consistency

Definition of Basically Available, Soft State, Eventual Consistency

Basically Available, Soft State, Eventual Consistency (BASE) is a database management approach that prioritizes availability over absolute consistency of data. Soft State reflects that the database state may change over time, even when no operations are applied. Eventual Consistency ensures that when no new updates are made, all replicas will eventually have the same data, although it may not be instantaneously.


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Key Takeaways

  1. Basically Available: This means that the system aims to remain available and function as expected even in cases of network failures or other unexpected events. It guarantees that every request will receive a response, although the response might not be accurate or up-to-date.
  2. Soft State: The state of the system might change over time, even without input. This is because nodes in the system may still be updating their data as they receive new information. A soft state enables the system to be highly distributed and resilient to failures, but at the cost of potentially providing stale data to clients.
  3. Eventual Consistency: This property of the system ensures that if no new updates are made for a certain period of time, eventually all nodes in the distributed system will converge to a consistent state. This is the main trade-off in the system, where consistency is sacrificed for high availability and partition tolerance.

Importance of Basically Available, Soft State, Eventual Consistency

The technology term Basically Available, Soft State, Eventual Consistency (BASE) is important because it represents a significant shift in the approach to data management and fault-tolerance in distributed systems.

Unlike traditional ACID (Atomicity, Consistency, Isolation, Durability) principles that prioritize strict transactional consistency, BASE focuses on providing high availability and scalability, sacrificing some level of immediate consistency.

This allows applications to gracefully handle failures and continue operating with reduced functionality, rather than stopping entirely.

By emphasizing a more relaxed consistency model, BASE enables developers to create systems capable of managing large volumes of data and supporting heavy workloads, which have become increasingly critical with the rise of cloud computing and the need for global-scale internet applications.


Basically Available, Soft State, Eventual Consistency (BASE) is a data management methodology tailored to address the needs of large-scale, distributed systems. Its primary purpose is to ensure that such systems work efficiently when spanning multiple nodes, while maintaining high availability and resiliency. Traditional approaches to data consistency, such as those employed by ACID properties (Atomicity, Consistency, Isolation, Durability), impose strict transactional rules, which can lead to performance bottlenecks and limited scalability in a distributed environment.

The BASE approach, on the other hand, emphasizes flexibility, working to achieve higher levels of performance, adaptability, and fault tolerance. This is particularly beneficial for applications that are more tolerant of occasional inconsistencies, such as social media platforms, e-commerce sites, and web-based collaboration tools. The three concepts encapsulated by BASE work together to achieve the desired balance of performance and consistency.

First, “Basically Available” ensures the system remains functional even in the presence of failures or network partitions, though some data may be temporarily inconsistent. Next, “Soft State” acknowledges that the system’s state may change, even without input, due to the ongoing process of asynchronously updating replicas. Finally, “Eventual Consistency” guarantees that, given enough time, all replicas will eventually converge to the same, consistent state.

This approach is used in systems like Amazon’s DynamoDB and Apache Cassandra, where it grants trade-offs among consistency, availability, and latency to better suit the specific needs of various applications. In sum, BASE serves as a practical means for managing large-scale, distributed systems, offering enhanced performance and fault tolerance for applications where minor inconsistencies can be tolerated.

Examples of Basically Available, Soft State, Eventual Consistency

Basically Available, Soft State, Eventual Consistency, also known as BASE, is a model that balances the trade-offs between data consistency and availability. It contrasts with the ACID model, which prioritizes strict consistency in database transactions. Here are three real-world examples of technologies or systems that employ BASE:

Amazon DynamoDB: Amazon’s managed NoSQL database, DynamoDB, uses the BASE model to offer high availability and low latency performance. It ensures that data updates are eventually propagated across all nodes in the distributed system, allowing the system to continue processing requests even with temporary inconsistencies. Additionally, the soft state feature facilitates high availability, while the system reaches eventual consistency through the use of optimistic replication and conflict resolution mechanisms.

Apache Cassandra: Apache Cassandra is a highly scalable, distributed NoSQL database designed for handling large quantities of data across many nodes. It follows the BASE model, emphasizing availability and partition tolerance over strict consistency. To achieve eventual consistency, it employs techniques such as tunable consistency levels, hinted handoff, and read repair. Cassandra is adopted by several organizations, such as Netflix, Spotify, and Twitter, for its high availability and fault-tolerance capabilities.

Conflict-Free Replicated Data Types (CRDTs): CRDTs are data structures that can be concurrently updated on multiple nodes in a distributed system and can be merged to achieve consistent results. They are designed specifically for systems that prioritize availability and partition tolerance. CRDT technology is employed in services such as collaboration tools, distributed databases, and edge computing platforms. Notable real-world applications that utilize CRDTs for conflict resolution and eventual consistency include Google’s collaboration suite (Google Docs, Sheets, Slides), Riak Database, and Automerge.

FAQ – Basically Available, Soft State, Eventual Consistency

What does “Basically Available” mean in distributed systems?

Basically Available refers to a system that guarantees availability even in the presence of failures. These systems are designed to handle requests even if some nodes or components have failed. Typically, this is achieved through replication and partition tolerance, allowing the system to provide a response even under adverse conditions.

What is a “Soft State” in distributed systems?

A Soft State refers to the transient or temporary nature of the data stored in a distributed system. It means that the system may experience changes to its state even when no inputs are given, due to external factors like data updates or node failures. Soft state is used to handle inconsistencies and temporary failures in a distributed system, with the expectation that the system will eventually converge to a consistent state.

What is “Eventual Consistency” in distributed systems?

Eventual Consistency is a consistency model used in distributed systems that prioritize availability and partition tolerance. It guarantees that, given enough time without any new updates, all nodes or replicas in the system will eventually converge to the same state, even in the face of temporary inconsistencies. This allows the system to continue functioning despite inconsistencies and provides a high level of availability, as long as the system is given enough time to converge.

What are the benefits of using systems with Basically Available, Soft State, and Eventual Consistency?

Systems that employ Basically Available, Soft State, and Eventual Consistency prioritize availability and partition tolerance, making them suitable for handling large amounts of data and traffic. These systems provide continuous operation even under failures and network partitions, allowing for fast response times and high performance. They are particularly useful for applications where temporary inconsistencies are tolerable, such as social networks, search engines, and caching systems.

What are the trade-offs in using systems with Basically Available, Soft State, and Eventual Consistency?

One trade-off of using such systems is that they may sacrifice consistency to maintain availability and fault tolerance. This may result in temporary inconsistencies during data propagation across nodes, which can be a concern for certain applications that require immediate consistency. Additionally, the management and design of these systems can be more complex due to their distributed nature and the need to handle consistency and state convergence.

Related Technology Terms

  • Data Replication
  • High Availability
  • Distributed Systems
  • Conflict Resolution
  • Event-driven Architecture

Sources for More Information


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