Table compression can optimize reads 

Configure data compression on a per-table basis to optimize performance of read-dominated tasks.

Search nodes typically engage in read-dominated tasks, so maximizing storage capacity of nodes, reducing the volume of data on disk, and limiting disk I/O can improve performance. In Cassandra 1.0 and later, you can configure data compression on a per-table basis to optimize performance of read-dominated tasks.

Configuration affects the compression algorithm for compressing SSTable files. For read-heavy workloads, such as those carried by Enterprise Search, LZ4 compression is recommended. Compression using the LZ4 compressor is enabled by default when you create a table. You can change compression options using CQL. Developers can also implement custom compression classes using the org.apache.cassandra.io.compress.ICompressor interface. You can configure the compression chunk size for read/write access patterns and the average size of rows in the table.