The Select all query works fine in a Cassandra KeySpace-Column Family. But when the Select by Key query is issued for a specific key, the FluentCassandra client throws a timeout exception. This happens for some of the keys in the same column family , while others succeed.
Could this be due to an index issue.
Okay,
I provided no further information about your issue. But since I had the same issue and stumbled upon this question here is what happened to me.
I followed @Richard suggestion and took a look on cassandra logs while the query was executed. I turned out that some non existent data file was being referenced.
Restarting Cassasandra forced the system to check its logs and rebuild the data files solving the issue.