Query integration in non-relational databases and achieving high availability in the cloud

Non-relational databases NoSQL offer in combination with cloud computing abilities to store and manage large amounts of data. Querying over multiple NoSQL databases and system scalability can be major challenges. To solve the integration of queries over different types of NoSQL databases, we have implemented the approach of converting documents into RDF/XML formats and advertising them on the endpoint. By using common query language SPARQL (SPARQL Protocol and RDF Query Language), we have shown the method of query integration over two different types of non-relational NoSQL databases, MongoDB and Neo4j. To accelerate the execution of read operations, we have proposed an architecture using the sharding method. We have analyzed the impact of vertical or horizontal scalability of the system. We have stored data on distributed storage and measured the time. We have found out that the shrading method improves the read operations time, while the time for write operations slightly increases. We have demonstrated both approaches, query integration and shrading method, on an example