NoSQL AMazon ec2 (Any suggestions?)
Full disclosure: I am the primary developer for MongoDB. (Also, I fully disclose for jbellis: he is the main developer for Cassandra.)
I prefer Mongo to the other databases out there because it is not only the simplest of them all, but it also has many features (geospatial indexing, easy file storage, secondary indexes, incl. And incl.) And is incredibly fast.
Scaling out is ~ 1 month from production ready, but people are already using it successfully. I just talked to MongoSF where a developer created a cluster of 25 EC2 instances processing 8M operations per second!
MongoDB mailing list is very active and helpful if you have any questions.
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Now the author of ThruDB is using Cassandra. (See for example his Cassandra backend for Lucene, http://github.com/tjake/Lucandra ).
Vs MongoDB, mongo is easier to pick up (very close to "schemaless mysql") but does not scale. Cassandra scales, but the data model is more complex for most people.
Some starting points at http://wiki.apache.org/cassandra/ArticlesAndPresentations
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I tried using Mongo DB for a couple of days. The initial experience is great, but I ended up having a performance issue too.
Mongo DB performance drops when you have too many records. What I mean by too many is over 10 million entries. (I think you generally won't have that many records.)
I am not trying to use Mongo DB replication feature. I am currently using Amazon EC2 and I am still struggling with the costs of running more servers. (Especially Mongo requires me to use a 64-bit platform to get past the 2GB limits.)
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