The thesis deals with a NewSQL database called CockroachDB. The aim of the thesis is to describe key concepts used in NewSQL databases and then evaluate and compare performance of the new database CockroachDB and the well-established PostgreSQL database. NewSQL databases are built for distributed environments and integrate the properties of both SQL and NoSQL databases. NewSQL databases use the standard SQL query language for interaction with a database. They use ACID transactions that guarantee high data consistency. They enable easier horizontal scaling, replication, high availability and automatic failover. The results of simple queries showed that CockroachDB achieves on average 5 times lower throughput and 3 times higher latency compared to PostgreSQL on three node cluster. Furthermore, CockroachDB provides only basic support for join operations.