Functional Differences: Amazon Keyspaces (for Apache Cassandra) versus Apache Cassandra

Following are the functional differences between Amazon Keyspaces and Apache Cassandra.

Cluster Configuration

Amazon Keyspaces is serverless, so there are no clusters, hosts, or Java virtual machines (JVMs) to configure. Cassandra’s settings for compaction, compression, caching, garbage collection, and bloom filtering are not applicable to Amazon Keyspaces and are ignored if specified.

Asynchronous Creation and Deletion of Keyspaces and Tables

Amazon Keyspaces performs data definition language (DDL) operations, such as creating and deleting keyspaces and tables, asynchronously. You can monitor the creation status of new resources in the AWS Management Console, which will indicate when a resource is pending or active. You can also monitor the creation status of a new resource programmatically by using the system schema table. A resource will become visible in the system schema once it is ready for use. The recommended design pattern to check when a new resource is ready for use is to poll the Amazon Keyspaces system schema tables (system_schema_mcs.*). For a list of DDL statements, see DDL Statements (Data Definition Language) in Amazon Keyspaces.

The following query shows whether a table has been successfully created.

SELECT keyspace_name, table_name, status FROM system_schema_mcs.tables WHERE keyspace_name = 'mykeyspace' AND table_name = 'mytable';

The output of the query looks like the following.

keyspace_name | table_name | status
--------------+------------+--------
   mykeyspace |    mytable | ACTIVE
            
        

System Tables

Amazon Keyspaces populates the system tables required by Apache 2.0 open source Cassandra drivers. The system tables visible to a client contain information unique to the authenticated user. The system tables are fully controlled by Amazon Keyspaces and are read-only.

Load Balancing

The system.peers table entries correspond to Amazon Keyspaces load balancers. For best results, we recommend using a round robin load-balancing policy and tuning the number of connections per IP to suit your applications needs.

CQL Query Throughput Tuning

Amazon Keyspaces supports up to 3000 CQL queries per TCP connection per second, but there is no limit on the number of connections a driver can establish. Most open source Cassandra drivers establish a connection pool to Cassandra and load balance queries over that pool of connections. Amazon Keyspaces exposes 9 peer IP addresses to drivers, and the default behavior of most drivers is to establish a single connection to each peer IP address. Therefore, the maximum CQL query throughput of a driver using the default settings will be 27000 CQL queries per second. To increase this number, we recommend increasing the number of connections per IP address your driver is maintaining in its connection pool. For example, setting the maximum connections per IP address to 2 will double the maximum throughput of your driver to 54000 CQL queries per second.

Range Delete

Amazon Keyspaces supports deleting items in range. A range deletion is limited to 1,000 rows in a single command. A range delete is atomic, but it is not isolated.

Batch

Amazon Keyspaces supports unlogged batch commands with up to 30 commands in the batch. Only unconditional INSERT, UPDATE, or DELETE commands are permitted in a batch. Logged batches are not supported.

Lightweight Transactions

Amazon Keyspaces (for Apache Cassandra) fully supports compare and set functionality on INSERT and UPDATE commands, which are known as lightweight transactions (LWTs) in Apache Cassandra. As a serverless offering, Amazon Keyspaces (for Apache Cassandra) provides consistent performance at any scale, including for lightweight transactions. With Amazon Keyspaces, there is no performance penalty for using lightweight transactions.

Authentication and Authorization

Amazon Keyspaces (for Apache Cassandra) uses AWS Identity and Access Management (IAM) for user authentication and authorization, and supports the equivalent authorization policies as Apache Cassandra. As such, Amazon Keyspaces does not support Apache Cassandra's security configuration commands.

Apache Cassandra APIs, Operations, and Data Types

Amazon Keyspaces supports all commonly used Cassandra data-plane operations, such as creating keyspaces and tables, reading data, and writing data. To see what is currently supported, see Supported Cassandra APIs, Operations, and Data Types in Amazon Keyspaces (for Apache Cassandra).

Empty Strings

Amazon Keyspaces supports empty strings and blob values. However, empty strings and blobs are not supported as clustering column values.