Explanation of BASE terminology

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The BASE acronym is used to describe the properties of certain databases, usually NoSQL databases. It's often referred to as the opposite of ACID.

There are only few articles that touch upon the details of BASE, whereas ACID has plenty of articles that elaborate on each of the atomicity, consistency, isolation and durability properties. Wikipedia only devotes a few lines to the term.

This leaves me with some questions about the definition:

Basically Available, Soft state, Eventual consistency

I have interpreted these properties as follows, using this article and my imagination:

Basically available could refer to the perceived availability of the data. If a single node fails, part of the data won't be available, but the entire data layer stays operational.

  • Is this interpretation correct, or does it refer to something else?
  • Update: deducing from Mau's answer, could it mean the entire data layer is always accepting new data, i.e. there are no locking scenarios that prevent data from being inserted immediately?

Soft state: All I could find was the concept of data needing a period refresh. Without a refresh, the data will expire or be deleted.

  • Automatic deletion of data in a database seems strange to me.
  • Expired or stale data makes more sense. But this concept would apply to any type of redundant data storage, not just NoSQL. Does it describe something else then?

Eventual consistency means that updates will eventually ripple through to all servers, given enough time.

  • This property is clear to me.

Can someone explain these properties in detail?

Or is it just a far-fetched and meaningless acronym that refers to the concepts of acids and bases as found in chemistry?

base-db definition nosql terminology database
6 Answers

  • Basic Availability: The database appears to work most of the time.

  • Soft State: Stores don’t have to be write-consistent or mutually consistent all the time.

  • Eventual consistency: Data should always be consistent, with regards how any number of changes are performed.

user_98449620

ACID and BASE are consistency models for RDBMS and NoSQL respectively. ACID transactions are far more pessimistic i.e. they are more worried about data safety. In the NoSQL database world, ACID transactions are less fashionable as some databases have loosened the requirements for immediate consistency, data freshness and accuracy in order to gain other benefits, like scalability and resiliency.

BASE stands for -

  • Basic Availability - The database appears to work most of the time.
  • Soft-state - Stores don't have to be write-consistent, nor do different replicas have to be mutually consistent all the time.
  • Eventual consistency - Stores exhibit consistency at some later point (e.g., lazily at read time).

Therefore BASE relaxes consistency to allow the system to process request even in an inconsistent state.

Example: No one would mind if their tweet were inconsistent within their social network for a short period of time. It is more important to get an immediate response than to have a consistent state of users' information.

user_3497100

To add to the other answers, I think the acronyms were derived to show a scale between the two terms to distinguish how reliable transactions or requests where between RDMS versus Big Data.

From this article acid vs base

In Chemistry, pH measures the relative basicity and acidity of an aqueous (solvent in water) solution. The pH scale extends from 0 (highly acidic substances such as battery acid) to 14 (highly alkaline substances like lie); pure water at 77° F (25° C) has a pH of 7 and is neutral.

Data engineers have cleverly borrowed acid vs base from chemists and created acronyms that while not exact in their meanings, are still apt representations of what is happening within a given database system when discussing the reliability of transaction processing.

One other point, since I having been working with Big Data using Elasticsearch it would help if I explained how it is structured. An instance of Elasticsearch is a node and a group of nodes form a cluster.

To me, from a practical standpoint, BA (Basically Available), in this context, has the idea of multiple master nodes to handle the Elasticsearch cluster and it's operations.

If you have 3 master nodes and the currently directing master node goes down, the system stays up, albeit in a less efficient state, and another master node takes its place as the main directing master node. If two master nodes go down, the system still stays up and the last master node takes over.

user_5435720
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