CockroachDB is a distributed SQL database built on a transactional and strongly-consistent key-value store. It scales horizontally; survives disk, machine, rack, and even datacenter failures with minimal latency disruption and no manual intervention; supports strongly-consistent ACID transactions; and provides a familiar SQL API for structuring, manipulating, and querying data.
CockroachDB is inspired by Google’s Spanner and F1 technologies, and it’s completely open source.
At the lowest level, CockroachDB is a distributed, strongly-consistent, transactional key-value store, but the external API is Standard SQL with extensions. This provides developers familiar relational concepts such as schemas, tables, columns, and indexes and the ability to structure, manipulate, and query data using well-established and time-proven tools and processes. Also, since CockroachDB supports the PostgreSQL wire protocol, it’s simple to get your application talking to Cockroach; just find your PostgreSQL language-specific driver and start building.
For more details, learn our basic CockroachDB SQL statements, explore the full SQL grammar, and try it out via our built-in SQL client. Also, to understand how CockroachDB maps SQL table data to key-value storage and how CockroachDB chooses the best index for running a query, see SQL in CockroachDB and Index Selection in CockroachDB.
CockroachDB supports the PostgreSQL wire protocol, so you can use any available PostgreSQL client drivers. We’ve tested it from the following languages:
CockroachDB uses the PostgreSQL wire protocol because it is better documented than the MySQL protocol, and because PostgreSQL has a liberal Open Source license, similar to BSD or MIT licenses, whereas MySQL has the more restrictive GNU General Public License.
Note, however, that the protocol used doesn’t significantly impact how easy it is to port applications. Swapping out SQL network drivers is rather straightforward in nearly every language. What makes it hard to move from one database to another is the dialect of SQL in use. CockroachDB’s dialect is based on PostgreSQL as well.
CockroachDB is well suited for applications that require reliable, available, and correct data regardless of scale. It is built to automatically replicate, rebalance, and recover with minimal configuration and operational overhead. Specific use cases include:
CockroachDB scales horizontally with minimal operator overhead. You can run it on your local computer, a single server, a corporate development cluster, or a private or public cloud. Adding capacity is as easy as pointing a new node at the running cluster.
At the key-value level, CockroachDB starts off with a single, empty range. As you put data in, this single range eventually reaches a threshold size (64MB by default). When that happens, the data splits into two ranges, each covering a contiguous segment of the entire key-value space. This process continues indefinitely; as new data flows in, existing ranges continue to split into new ranges, aiming to keep a relatively small and consistent range size.
When your cluster spans multiple nodes (physical machines, virtual machines, or containers), newly split ranges are automatically rebalanced to nodes with more capacity. CockroachDB communicates opportunities for rebalancing using a peer-to-peer gossip protocol by which nodes exchange network addresses, store capacity, and other information.
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