  Cassandra is a popular structured storage system with high-performance,
scalability and high availability, and is usually used to store data that has
some sortable attributes. When deploying and configuring Cassandra, it is
important to design a suitable schema of column families for accelerating the
target queries. However, one schema is only suitable for a part of queries, and
leaves other queries with high latency.
  In this paper, we propose a new replica mechanism, called heterogeneous
replica, to reduce the query latency greatly while ensuring high write
throughput and data recovery. With this replica mechanism, different replica
has the same dataset while having different serialization on disk. By
implementing the heterogeneous replica mechanism on Cassandra, we show that the
read performance of Cassandra can be improved by two orders of magnitude with
TPC-H data set.
