All secondary indexes (2i, SAI, and SASI) are built in the background automatically, without blocking reads or writes. Client-maintained tables as indexes must be created manually. For example, if the age column had been indexed by creating a table such as cyclist_by_age, your client application would have to populate the table with data from the cyclist_name table that uses id as the primary key.

To perform a hot rebuild of an index, use the nodetool rebuild_index command.