From what I've read zBase is a fork of Membase. So zBase is a direct competitor to Couchbase which is what Membase became.
One of the main advantage of zBase / Membase / Couchbase compared to many other NoSQL data stores is their strict consistency model (compared to eventual consistency in Riak for example).
This means that with a zBase/Membase/Couchbase cluster, if client A writes a new value to a key in the cluster and client B reads from the same key immediately afterwards, client B is guaranteed to (immediately) see what client A wrote.
While in eventual consistency models, client B might see the old value in that case (could be because the change might not have propagated to all servers in the cluster yet). If client B tried to read again a few minutes later he might then see the new value from A.
Strict consistency is required in a lot of applications such as game servers (which is why Zynga needs it).
For use cases that are more read-heavy, like holding the contents of a news website, eventual consistency is good enough.
One of the main advantage of zBase / Membase / Couchbase compared to many other NoSQL data stores is their strict consistency model (compared to eventual consistency in Riak for example).
This means that with a zBase/Membase/Couchbase cluster, if client A writes a new value to a key in the cluster and client B reads from the same key immediately afterwards, client B is guaranteed to (immediately) see what client A wrote.
While in eventual consistency models, client B might see the old value in that case (could be because the change might not have propagated to all servers in the cluster yet). If client B tried to read again a few minutes later he might then see the new value from A.
Strict consistency is required in a lot of applications such as game servers (which is why Zynga needs it).
For use cases that are more read-heavy, like holding the contents of a news website, eventual consistency is good enough.