Get started with queries in Cassandra drivers

Most Cassandra drivers can execute queries against a database synchronously or asynchronously. The appropriate choice for your application depends on your use cases and requirements.

This means that the application sends a query to the database, and then the thread that sent the query waits for the query to complete before proceeding. In multi-threaded applications, other threads can continue to run while the query is processed. In single-threaded applications, this can block the entire application while waiting for the query result.

With synchronous query execution, it is easy to tell when a query completes, and this can make the application’s execution logic easier to follow. However, each thread can only execute one query at a time. While server nodes usually take less than a millisecond to fulfill a request, throughput can degrade when executing extremely large numbers of queries or while waiting for long-running queries to finish. If your application needs to process thousands or millions of queries, asynchronous query execution can be more performant.

Consistency levels determine how many replicas in a cluster must acknowledge a read or write operation before it is considered successful. For more information about consistency levels, see the documentation for your driver:

When executing queries, you often need to convert between the data types used in your application and the CQL data types used in the database. For more information about type conversion, see the documentation for your driver:

To learn more about query execution with Cassandra drivers, explore your driver’s documentation and the other driver topics in the HCD documentation. For example: