Confluent Cloud

Confluent Cloud ksqlDB

ksqlDB is a database purpose-built to help developers create stream processing applications on top of Apache Kafka®. Confluent Cloud provides a fully managed solution for creating and managing ksqlDB clusters.

You can provision ksqlDB clusters by using the Confluent Cloud Console or the Confluent CLI.

For more information, see Confluent Cloud ksqlDB Quick Start.

Supported Features for ksqlDB in Confluent Cloud

  • Web interface for managing your ksqlDB cloud environment directly from your browser that exposes all critical ksqlDB information.
  • SQL editor to write, develop, and execute SQL queries with auto completion directly from the Web interface.
  • Integration with Confluent Cloud Schema Registry to leverage your existing schemas to use within your SQL queries.
  • SQL-based Connect integration.
  • Available in AWS, GCP, and Azure in all regions.

New Features for ksqlDB in Confluent Cloud

For the latest features in ksqlDB, see the 0.26.0 changelog.

Limitations for ksqlDB in Confluent Cloud

  • Currently, user-defined functions (UDFs, UDAFs, and UDTFs) aren’t supported. For more information, see Functions.
  • You can have a maximum of 20 persistent queries per cluster.
  • You can have a maximum of 10 ksqlDB clusters. For more information, see Create a ksqlDB cluster in Confluent Cloud.
  • Pull queries have specific limitations in Confluent Cloud. For more information, see Pull queries in Confluent Cloud.
  • ccloud CLI version 0.198.0 or higher is required to create ksqlDB API keys for Confluent Cloud.

Pricing for ksqlDB in Confluent Cloud

The unit of pricing in Confluent Cloud ksqlDB is the Confluent Streaming Unit. A Confluent Streaming Unit is an abstract unit that represents the linearity of performance. For example, if a workload gets a certain level of throughput with 4 CSUs, you can expect about three times the throughput with 12 CSUs.

Confluent charges you in CSUs per hour.

You select the number of CSUs for your cluster at provisioning time. You can configure CSUs as follows:

  • 1 CSU is the minimum.
  • 12 CSUs is the maximum.
  • Your cluster can have 1, 2, 4, 8, or 12 CSUs.
  • Clusters with 8 or 12 CSUs are automatically configured for high availability.
  • High availability cannot be enabled for clusters with less than 8 CSUs.


Confluent Streaming Unit pricing varies slightly depending on cloud provider and region. Pricing is shown in the web interface as part of ksqlDB provisioning so that you can see exact pricing for your cloud and region of choice.

Scaling CSUs for ksqlDB in Confluent Cloud

Scaling your clusters’s CSUs after initial provisioning is not currently supported. If you determine that your cluster requires more CSUs, you must provision a new cluster with the desired number of CSUs, and migrate to your new one.

Sizing guidelines for ksqlDB in Confluent Cloud

The number of CSUs needed for your cluster depends on the workload, including the number of queries, query complexity, and throughput. The amount of resources allocated to a cluster is proportional to the number of CSUs defined for the cluster.

Four CSUs are sufficient for many workloads. In general, start with four CSUs and scale out if more capacity is needed, or scale down if less capacity is needed. To identify when more CSUs are needed, check the ksqlDB consumer lag or the CSU Saturation metric. For more information, see Monitor persistent queries.

After your ksqlDB cluster is provisioned, you can only change the Confluent Streaming Unit cluster by migrating to a new one one with the desired number of CSUs.