What is the difference between Cassandra and CouchDB?

Question

I\'m looking at both projects and I can\'t really see the difference

from Cassandra Site:

Cassandra is a highly scalable, eventually consistent,

Answer 1

CouchDB is a document store. You put documents (JSON objects) in it and define views (indexes) over them. The objects can be arbitrarily complex with potentially deep structure. Further, they are not constrained to following some consistent schema.

Cassandra is a ragged-table key-value store. It just stores rows, each of which has a set of named columns grouped in to families with values. It sounds quite close to BigTable; BigTable doesn't require each row to have the same structure (unlike an SQL database). The values may have some structure, but this kind of store doesn't know anything about that -- they're just strings/byte sequences.

Yes, they are both non-relational databases, and there is probably a fair amount of overlap in their applicability, but they do have distinctly different data organization models. Each can probably be forced into emulating the other, but each model will map best to a different set of problems.

Answer 2

CouchDB has a feature present in very few open source database technologies: offline replication. CouchDB is designed so that applications can be run at the edge of the network. These applications are available even when internet connectivity fails.

Offline replication can also be leveraged to build large clusters, but CouchDB is designed to be robust and simple whether it is running on a single server, a datacenter, or even a smartphone.