Since 2.1.0-rc2, it appears that the secondary indexes are not always working. Immediately after the INSERT of a row, the index seems to be there. But after a while (I do not know when or why), SELECT statements based on any secondary index do not return the corresponding row(s) anymore. I noticed that a restart of C* may have an impact (the data inserted before the restart may be seen through the index, even if it was not returned before the restart).
Here is a use-case example (in order to clarify my request) :
The last SELECT statement may or may not return a row depending on the instant of the request. I experienced that with 2.1.0-rc5 through CQLSH with clusters of one and two nodes. Since it depends on the instant of the request, I am not able to deliver any way to reproduce that systematically (It appears to be linked with some scheduled job inside C*).