BASE is:
Basically available: The database system always seems to
work. Basically available indicates that the system does guarantee
Availability, in terms of the CAP theorem. NoSQL databases spread
data across many storage systems with a high degree of replication
for high degree of Availability.
Soft state: With Soft start, the copies of a data item may be
inconsistent and the state of the system may change over time,
even without input because of the ‘‘Eventual Consistency’’.
‘‘The soft state mode should be utilized for applications built
on legacy functionality in the backend, particularly when the
functionality includes initial loading/caching of large sums of
information for a single request. By using soft state, the resources/functionality
which has been loaded during the initial load
can be reused for the subsequent requests of the service’’ [8].
Eventually consistent: The updates propagate, when there are
no updates over a certain period of time defied for a particular
application. Hence, the systems where BASE is the key requirement
for reliability, the potential of the data changes essentially slows
down.
A lot of databases on websites prefer Speed, Performance and
Scalability instead of pure Consistency and integrity of data. Availability
of BASE system is ensured through accepting partial partitions.
Protocols such as Gossip can be used to replicate data optimistically
and later heal any problems that arise [9]. ‘‘Updates
are applied in the first-tier, but then passed to inner-tier services
which might apply them in different orders’’ [9].
The elasticity of storage and server resources is at the crux of
BASE paradigm. BASE databases use strategies to have Consistency,
Atomicity and Partition tolerance ‘‘eventually’’. BASE does not flout
CAP theorem, but works around it. If users are partitioned across
five database servers, BASE design encourages crafting operations
in such a way that a user database failure impacts only the 20% of
the users on that particular host.
The following subsections discuss about the BASE properties of
some of the mostly used NoSQL.