<!-- *********************************************************** -->
<!-- string replacements for cluster limits throughout the topic -->
<!-- *********************************************************** -->
<!-- cluster limits: -->
<!-- eCKU/CKU limits -->
<!-- string replacements for min/max eCKU/CKU values throughout the topic -->

<a id="cloud-cluster-types"></a>

# Kafka Cluster Types in Confluent Cloud

Confluent offers different types of Apache Kafka® clusters in Confluent Cloud. The cluster
type you choose determines the features, capabilities, and price of the
cluster. Use the information in this topic to find the cluster with the
features and capabilities that best meet your needs.

<a id="basic-cluster"></a>

<a id="standard-cluster"></a>

<a id="enterprise-cluster"></a>

<a id="dedicated-cluster"></a>

<a id="freight-cluster"></a>

| Cluster type   | Best for                                                                                                                                |
|----------------|-----------------------------------------------------------------------------------------------------------------------------------------|
| Basic          | Development, testing, and basic use cases.                                                                                              |
| Standard       | Production workloads that use public networking.                                                                                        |
| Enterprise     | Production workloads that require private networking.                                                                                   |
| Dedicated      | High-throughput or private-networking workloads that need dedicated<br/>capacity and manual scaling.                                    |
| Freight        | Cost-optimized, high-throughput workloads that tolerate relaxed<br/>latency and are less expensive than self-managed open source Kafka. |

## Features

All clusters have the following features:

- [Kafka ACLs](../security/access-control/acls/overview.md#acl-manage)
- [Fully managed replica placement](resilience.md#confluent-cloud-resilience)
- [User interface to manage consumer lag](../monitoring/monitor-lag.md#cloud-monitoring-lag)
- [Topic management](../topics/overview.md#cloud-topics-manage)
- [Fully managed connectors](../connectors/overview.md#kafka-connect-cloud)
- [View and consume Connect logs](../connectors/logging-cloud-connectors.md#ccloud-connector-logging)
- [Stream Governance](../stream-governance/index.md#cloud-dg)
- [Stream Catalog](../stream-governance/stream-catalog.md#cloud-stream-catalog)
- [Stream Lineage](../stream-governance/stream-lineage.md#cloud-stream-lineage)
- [Encryption-at-rest](https://confluent.safebase.us/?itemUid=ef061e5b-a2f4-469e-92bc-ab973e3d7842&source=title)
- [TLS for data in transit](../security/encrypt/tls.md#manage-data-in-transit-with-tls)
- [Role-based Access Control (RBAC)](../security/access-control/rbac/overview.md#cloud-rbac) (Basic clusters do not support RBAC roles for resources within the Kafka cluster)

### Feature comparison table

The tables below offer comparisons of the features supported by only some Kafka cluster types.

| Feature                                                                                                             | Basic   | Standard   | Enterprise     | Freight<br/><br/><br/>(AWS only)<br/><br/>   | Dedicated        |
|---------------------------------------------------------------------------------------------------------------------|---------|------------|----------------|----------------------------------------------|------------------|
| [Exactly Once Semantics](/platform/current/streams/concepts.html#streams-concepts-processing-guarantees)            | Yes     | Yes        | Yes            | No                                           | Yes              |
| [Key based compacted storage](/kafka/kafka/log_compaction.html)                                                     | Yes     | Yes        | Yes            | Yes                                          | Yes              |
| [Custom Connectors](../connectors/bring-your-connector/overview.md#cc-bring-your-connector)                         | Yes     | Yes        | Yes (AWS only) | No                                           | Yes              |
| [Flink](../flink/overview.md#ccloud-flink)                                                                          | Yes     | Yes        | Yes            | Yes<sub>†</sub>                              | Yes              |
| [Tableflow](../topics/tableflow/overview.md#cloud-tableflow)                                                        | Yes     | Yes        | Yes            | Yes                                          | Yes              |
| [ksqlDB](../ksqldb/overview.md#cloud-ksqldb-create-stream-processing-apps)                                          | Yes     | Yes        | No             | No                                           | Yes              |
| [Schema validation](../sr/broker-side-schema-validation.md#cloud-schema-validation)                                 | No      | No         | No             | No                                           | Yes              |
| [Stream Sharing](../stream-sharing/index.md#cloud-data-sharing)                                                     | Yes     | Yes        | No             | No                                           | Yes<sub>\*</sub> |
| [Public networking](../networking/overview.md#cloud-networking-support-public)                                      | Yes     | Yes        | No             | No                                           | Yes              |
| [Private networking](../networking/overview.md#cloud-networking-support-private)                                    | No      | No         | Yes            | Yes                                          | Yes              |
| [OAuth](../security/authenticate/workload-identities/identity-providers/oauth/overview.md#oauth-overview)           | No      | Yes        | Yes            | Yes                                          | Yes              |
| [Mutual TLS (mTLS)](../security/authenticate/workload-identities/identity-providers/mtls/overview.md#mtls-overview) | No      | No         | Yes (AWS only) | Yes                                          | Yes              |
| [Self-managed encryption keys](../security/encrypt/byok/overview.md#byok-encrypted-clusters)                        | No      | No         | Yes            | No                                           | Yes              |
| [Audit logs](../monitoring/audit-logging/cloud-audit-log-concepts.md#cloud-audit-logs)                              | No      | Yes        | Yes            | Yes                                          | Yes              |
| [Access Transparency](../monitoring/audit-logging/access-transparency-overview.md#access-transparency-overview)     | No      | No         | No             | No                                           | Yes              |
| [Automatic Elastic scaling](../billing/billing-dimensions.md#e-cku-definition)                                      | Yes     | Yes        | Yes            | Yes                                          | No               |
| [Client Quotas](client-quotas.md#client-quotas)                                                                     | No      | No         | Yes            | Yes                                          | Yes              |

\* Stream sharing doesn’t support all private networking options.

† Flink jobs writing to topics in Freight clusters may produce duplicate records in some failure scenarios. Freight does not currently support transactions, so exactly-once semantics is not available when writing to a Freight cluster. Reads from Freight clusters are not affected.

<a id="freight-limitations"></a>

#### Freight cluster considerations

- Freight clusters are currently available in select AWS regions. For more information, see [Confluent Cloud Regions and Availability by Cloud Provider](../regions/overview.md#providers-regions).
- You must optimize the clients you use to connect to Freight clusters. For more information, see [Freight Clients for Confluent Cloud](../client-apps/optimizing/freight.md#freight-latency-clients).
- Freight clusters do not support the following:
  - Idempotent producer
  - Transactions
- Freight clusters do not support the following metrics and functions:
  - `DELETE_RECORDS`
  - `REPLICA_STATUS`

### Cluster linking capabilities

The table below offers a comparison of cluster linking capabilities by cluster type.

| Cluster type                  | Basic   | Standard   | Enterprise          | Dedicated           | Freight   |
|-------------------------------|---------|------------|---------------------|---------------------|-----------|
| Supports source clusters      | Yes     | Yes        | Yes <sub>(\*)</sub> | Yes <sub>(\*)</sub> | Yes       |
| Supports destination clusters | No      | No         | Yes <sub>(\*)</sub> | Yes <sub>(\*)</sub> | Yes       |

\* Capability dependent on the networking type and the other cluster involved. To learn more, see [Supported cluster types](../multi-cloud/cluster-linking/index.md#cloud-cluster-linking-supported-types) in the Cluster Linking documentation.

### Uptime service level agreement options

The table below offers a comparison of uptime service level agreements (SLA) options by cluster type. For more information, see [Confluent Cloud Service Level Agreement](https://confluent.io/confluent-cloud-uptime-sla/).

Considerations:
: - To obtain a higher uptime SLA, you can upgrade from Basic to a Standard cluster at any time using the Cloud Console.
  - Standard and Enterprise clusters require 2 eCKU minimums for the 99.99% SLA.
  - Dedicated clusters require multi-zone deployments for the 99.99% SLA.

| Cluster type   | 99.5%   | 99.9%   | 99.95%              | 99.99%                |
|----------------|---------|---------|---------------------|-----------------------|
| Basic          | Yes     | No      | No                  | No                    |
| Standard       | No      | Yes     | No                  | Yes (Requires 2 eCKU) |
| Enterprise     | No      | Yes     | No                  | Yes (Requires 2 eCKU) |
| Dedicated      | No      | No      | Yes <sub>(SZ)</sub> | Yes <sub>(MZ)</sub>   |
| Freight        | No      | No      | No                  | Yes                   |

<a id="cluster-scale-overview"></a>

## Cluster provisioning and scaling

Confluent uses billing units to provision and scale clusters.

A Confluent Unit for Kafka (CKU) is the unit of throughput capacity for Dedicated
clusters in Confluent Cloud. Each CKU provides a fixed amount of ingress,
egress, partitions, and client connections. You scale a Dedicated
cluster by adding or removing CKUs. For more information, see
[Fixed limits and recommended guidelines](#cku-details).

An Elastic Confluent Unit for Kafka (eCKU) is the unit of throughput capacity for Basic,
Standard, Enterprise, and Freight clusters.
Unlike CKUs for Dedicated clusters, eCKUs scale
elastically—the cluster automatically adjusts capacity based on your
usage. For more information, see [eCKU](../billing/billing-dimensions.md#e-cku-definition) and
[eCKU/CKU comparison](#e-cku-details).

### Elastic scaling

Basic, Standard, Enterprise, and Freight clusters are elastic, shrinking and expanding
automatically based on load. You don’t resize these clusters (unlike Dedicated clusters). When you need more capacity, your
cluster expands up to the fixed ceiling. If you’re not using capacity above the minimum, you’re not paying for it. If you’re at zero
capacity, you don’t pay for anything.

To understand how your cluster scales over time, use the **eCKU usage** chart
on the **Cluster Overview > Monitor** tab in the Confluent Cloud Console. This chart shows the
eCKU count over time alongside the dimensions that drive eCKU scaling,
such as throughput, connections, and requests. The values for these dimensions
are normalized against your current maximum eCKU value, so as a dimension
approaches 1.0 (100%), it is likely driving eCKU scaling.

<a id="freight-scale-limitations"></a>

#### Freight cluster scaling considerations

Freight clusters are elastic, scaling automatically based on load, so
you only pay for the eCKUs you use. However, Freight clusters might
not scale as quickly as other eCKU clusters. In general, Freight
clusters can support an additional 4 eCKU of capacity (240 MBps of ingress
/ 720 MBps of egress) every 10 minutes. If your workload grows faster than
this, you might experience higher latency or failed requests. As your workload
decreases, you pay for your actual eCKU usage.

In scenarios where you expect a large, rapid increase in traffic, consider
contacting your account team to get Confluent to work with you to meet your
request.

<a id="fast-scaling-enterprise"></a>

### Fast scaling for Enterprise clusters

All Enterprise clusters support fast scaling up to 10 eCKU, which is similar to how elastic scaling has worked in the past. Beyond
10 eCKU, Enterprise clusters support *on-demand* scaling, which might be limited to a growth rate of approximately 20 minutes per
eCKU.

Considerations:
: - To provision Enterprise clusters with a maximum of 32 eCKU on AWS, your cluster networking must use Private Network Interface (PNI).
  - Enterprise clusters that use PrivateLink networking on AWS are limited to 10 eCKU.
  - Enterprise clusters that use PrivateLink networking on Google Cloud or Azure are limited to 32 eCKU.
  <br/>
  - If you have workloads that require fast scaling beyond 10 eCKU or workloads larger than 32 eCKU, contact Confluent to request
    to have your cluster enabled.

### Manual scaling

Dedicated clusters are provisioned and billed in terms of Confluent Unit for Kafka (CKU). CKUs are a unit of horizontal
scalability in Confluent Cloud that provide a preallocated amount of resources. How much you can ingest
and stream per CKU depends on a variety of factors including client application design and
partitioning strategy. For more information, see [Fixed limits and recommended guidelines](#cku-details).

## Cluster sizing

The following sections describe the minimum and maximum capacity you can provision for each cluster type.

<a id="min-max-ecku"></a>

### Minimum/maximum eCKU requirements

The table below lists minimum and maximum requirements for elastic cluster types. Dedicated clusters have CKU
limits that depend on billing and other factors. For more information, see [CKU purchase limits](#cku-limits-per-cluster).

Considerations:
: - To provision Enterprise clusters with a maximum of 32 eCKU on AWS, your cluster networking must use Private Network Interface (PNI).
  - Enterprise clusters that use PrivateLink networking on AWS are limited to 10 eCKU.
  - Enterprise clusters that use PrivateLink networking on Google Cloud or Azure are limited to 32 eCKU.
  <br/>
  - Enterprise clusters support fast scaling up to 10 eCKU and on-demand scaling beyond 10 eCKU. On-demand scaling
    might be limited to a growth rate of approximately 20 minutes per eCKU. For more information, see [Fast scaling for Enterprise clusters](#fast-scaling-enterprise).

| Cluster type   | Minimum eCKU                  |   Maximum eCKU |
|----------------|-------------------------------|----------------|
| Basic          | 1                             |             50 |
| Standard       | 1 (99.9% SLA), 2 (99.99% SLA) |             10 |
| Enterprise     | 1 (99.9% SLA), 2 (99.99% SLA) |             32 |
| Freight        | 2                             |            152 |

To help you control costs with elastic cluster types, you can set a lower maximum eCKU capacity on your elastic
cluster. When you lower the maximum eCKU, you lower the capacity of your cluster. Use this feature with caution.
The maximum eCKU limits the cluster’s capacity, which can lead to throttling or workload impact when the reduced
capacity limit is reached.

When you lower maximum eCKU to reduce the capacity of your cluster, you must also manage your workload, especially
for limits not currently strictly enforced. Confluent will contact you if your clusters with managed maximum eCKU
repeatedly exceed the user-defined reduced capacity for requests, total client connections, and connection
attempts. For more information about managing limits, see [Cluster limit comparison](#cluster-limits-compare). For information
about how to lower maximum eCKU, see [Update Kafka clusters](update-cluster.md#cloud-cluster-update-api).

<a id="cku-limits-per-cluster"></a>

### CKU purchase limits

Dedicated clusters can be purchased in any whole number of CKUs up to the limit.

- For organizations with credit card billing, the upper limit is 4 CKUs per Dedicated cluster.
  Clusters with higher CKU limits are available by request.
- For organizations with integrated cloud provider billing or payment using an invoice,
  the upper limit is 24 CKUs per Dedicated cluster. Clusters with higher CKU limits are available by request.

For clusters that require higher CKU limits, contact [Confluent Support](https://support.confluent.io) to discuss
the onboarding process and product considerations. <sub>\*</sub>

Single-zone clusters can have 1 or more CKUs, whereas multi-zone clusters, which are spread across three availability zones,
require a minimum of 2 CKUs. Zone availability cannot be changed after the cluster is created.

\* AWS supports Kafka clusters to 252 CKUs. Google Cloud supports Kafka clusters to 152 CKUs. Azure supports Kafka clusters to 100 CKUs.

<a id="e-cku-basic-details"></a>

<a id="e-cku-standard-details"></a>

<a id="e-cku-details"></a>

<a id="enterprise-cku-guidance"></a>

<a id="ecku-comparison-table"></a>

<a id="e-cku-freight-details"></a>

<a id="freight-ecku-guidance"></a>

## eCKU/CKU comparison

Use the table below to compare limits for a single billing unit for each cluster type. For more information, see [eCKU](../billing/billing-dimensions.md#e-cku-definition), [Minimum/maximum eCKU requirements](#min-max-ecku) and [Cluster provisioning and scaling](#cluster-scale-overview).

For Dedicated clusters, these per-CKU limits scale linearly as you add
or remove CKUs. For example, each extra CKU increases the Kafka REST Produce
v3 connection limit by
300 requests per
second.

| Dimension                                                                       | [Basic eCKU](#cluster-scale-overview)   | [Standard eCKU](#cluster-scale-overview)   | [Enterprise eCKU](#cluster-scale-overview)   |   [Dedicated CKU](#cluster-scale-overview) | [Freight eCKU](#cluster-scale-overview)   |
|---------------------------------------------------------------------------------|-----------------------------------------|--------------------------------------------|----------------------------------------------|--------------------------------------------|-------------------------------------------|
| [Ingress](../_glossary.md#term-ingress) (MBps)                                  | 5                                       | 25                                         | 60                                           |                                         60 | 60                                        |
| [Egress](../_glossary.md#term-egress) (MBps)                                    | 15                                      | 75                                         | 180                                          |                                        180 | 180                                       |
| [Partitions (pre-replication)](../_glossary.md#term-partitions-pre-replication) | 30                                      | 250                                        | 3,000                                        |                                      4,500 | 3,000                                     |
| Number of partitions that you can compact (pre-replication)                     | 30                                      | 250                                        | 1,000                                        |                                      4,500 | None                                      |
| [Total client connections](../_glossary.md#term-total-client-connections)       | 20                                      | 1000                                       | 18,000                                       |                                     18,000 | 18,000                                    |
| [Connection attempts](../_glossary.md#term-connection-attempts) (per second)    | 5                                       | 50                                         | 500                                          |                                        500 | 500                                       |
| [Requests](../_glossary.md#term-requests) (per second)                          | 100                                     | 1,500                                      | 7,500                                        |                                     15,000 | 15,000                                    |
| Kafka REST Produce v3 - Max throughput (MBps)                                   | Not applicable                          | Not applicable                             | Not applicable                               |                                         50 | Not applicable                            |
| Kafka REST Produce v3 - Max connection requests (per second) <sub>‡</sub>       | Not applicable                          | Not applicable                             | Not applicable                               |                                        300 | Not applicable                            |
| Kafka REST Produce v3 - Max streamed requests (per second)                      | Not applicable                          | Not applicable                             | Not applicable                               |                                       3000 | Not applicable                            |
| Kafka REST Admin v3 - Max connection requests (per second) <sub>‡</sub>         | Not applicable                          | Not applicable                             | Not applicable                               |                                        300 | Not applicable                            |

‡ Connection request limits are enforced per cluster and IP address for elastic cluster types.

#### IMPORTANT
Compacted partitions count toward the partition limit for each billing
unit (eCKU or CKU). For Basic, Standard, and
Dedicated clusters, the compacted limit equals the partition
limit, so each billing unit supports up to its full partition count
whether or not the partitions are compacted. Enterprise clusters
have a lower compacted limit: of the 3,000
partitions each eCKU supports, up to
1,000 can be compacted.
Exceeding either limit requires an additional eCKU.

<a id="cluster-limits-compare"></a>

## Cluster limit comparison

Use the table below to compare cluster limits across cluster types.

<!-- note that the REST API limits are also noted in the docs-cloud/kafka-rest/kafka-rest-cc.rst topic, so changes should
be duplicated there. -->

Considerations:
: - To provision Enterprise clusters with a maximum of 32 eCKU on AWS, your cluster networking must use Private Network Interface (PNI).
  - Enterprise clusters that use PrivateLink networking on AWS are limited to 10 eCKU.
  - Enterprise clusters that use PrivateLink networking on Google Cloud or Azure are limited to 32 eCKU.
  <br/>
  - Basic, Standard, Enterprise, and Freight cluster limits are based on maximum eCKU for the cluster type. For more information, see [eCKU](../billing/billing-dimensions.md#e-cku-definition).
  - Dedicated Kafka cluster limits vary by cloud provider (see the preceding footnote). For more information, see [CKU purchase limits](#cku-limits-per-cluster) and [CKU](../billing/billing-dimensions.md#cku-definition).
  - For connector tasks per cluster, Basic clusters are limited to one task per connector. You can deploy 250 connectors to a Basic cluster but each
    connector can only have one task. If you need more than one task, upgrade your cluster.
  - Enterprise clusters support fast scaling up to 10 eCKU and on-demand scaling beyond 10 eCKU. On-demand scaling
    might be limited to a growth rate of approximately 20 minutes per eCKU. For more information, see [Fast scaling for Enterprise clusters](#fast-scaling-enterprise).

| Dimension                                                                 | [Basic](#basic-cluster)   | [Standard](#standard-cluster)   | [Enterprise](#enterprise-cluster)   | [Dedicated](#dedicated-cluster)   | [Freight](#freight-cluster)   |
|---------------------------------------------------------------------------|---------------------------|---------------------------------|-------------------------------------|-----------------------------------|-------------------------------|
| [Maximum eCKU/CKU](#min-max-ecku)                                         | 50                        | 10                              | 32                                  | 252<sub>†</sub>                   | 152                           |
| Fast scaling                                                              | Not applicable            | Not applicable                  | 10                                  | Not applicable                    | Not applicable                |
| Ingress (MBps)                                                            | 250                       | 250                             | 1,920                               | 9,120                             | 9,120                         |
| Egress (MBps)                                                             | 750                       | 750                             | 5,760                               | 27,360                            | 27,360                        |
| Partitions (pre-replication)                                              | 1500                      | 2500                            | 96,000                              | 100,000                           | 50,000                        |
| Number of partitions you can compact                                      | 1500                      | 2500                            | 32,000                              | 100,000                           | None                          |
| Total client connections                                                  | 1000                      | 10,000                          | 576,000                             | 2,736,000                         | 2,736,000                     |
| Connection attempts (per second)                                          | 250                       | 500                             | 16,000                              | 76,000                            | 76,000                        |
| Requests (per second)                                                     | 5,000                     | 15,000                          | 240,000                             | 2,280,000                         | 2,280,000                     |
| Message size (MB)                                                         | 8                         | 8                               | 20                                  | 20                                | 20                            |
| Client version (minimum)                                                  | 0.11.0                    | 0.11.0                          | 0.11.0                              | 0.11.0                            | 0.11.0                        |
| Request size (MB)                                                         | 100                       | 100                             | 100                                 | 100                               | 100                           |
| Fetch bytes (MB)                                                          | 55                        | 55                              | 55                                  | 55                                | 55                            |
| API keys                                                                  | 50                        | 250                             | 2,500                               | 20,000                            | 2,500                         |
| Partition creation and deletion (per five minute period)                  | 250                       | 500                             | 500                                 | 5,000                             | 500                           |
| Connector tasks per Kafka cluster                                         | 250                       | 250                             | 250                                 | 250                               | Not applicable                |
| ACLs                                                                      | 1,000                     | 1,000                           | 4,000                               | 10,000                            | 10,000                        |
| Kafka REST Produce v3 - Max throughput (MBps)                             | 10                        | 10                              | 10                                  | 7,600                             | 10                            |
| Kafka REST Produce v3 - Max connection requests (per second) <sub>‡</sub> | 25                        | 25                              | 25                                  | 45,600                            | 25                            |
| Kafka REST Produce v3 - Max streamed requests (per second)                | 1000                      | 1000                            | 1000                                | 456,000                           | 1000                          |
| Kafka REST Produce v3 - Max message size for Kafka REST Produce API (MB)  | 8                         | 8                               | 8                                   | 20                                | 8                             |
| Kafka REST Admin v3 - Max connection requests (per second) <sub>‡</sub>   | 25                        | 25                              | 25                                  | 45,600                            | 25                            |

† The maximum CKU limit for Dedicated clusters varies by cloud provider: AWS supports up to 252 CKUs, Google Cloud supports up to 152 CKUs, and Azure supports up to 100 CKUs (available by request).

‡ Connection request limits are enforced per cluster and IP address for elastic cluster types.

#### IMPORTANT
Compacted partitions count toward the total partition limit, and the
limit is enforced per billing unit (eCKU or CKU). For Basic,
Standard, and Dedicated clusters, the compacted limit
equals the partition limit. Enterprise clusters have a lower
compacted limit: of the 96,000 partitions a cluster
supports, up to 32,000 can be compacted.
Exceeding the per-eCKU compacted limit
(1,000) requires an additional
eCKU, even when the total partition count is within range.

The capabilities provided in this topic are for planning purposes,
and are not a guarantee of performance, which varies depending on
each unique configuration.

<a id="cluster-limits-enforcement"></a>

### Request and connection limit enforcement

Confluent doesn’t currently strictly enforce the maximum limits for requests,
total client connections, and connection attempts on Basic, Standard, Enterprise, Dedicated, and Freight clusters.
This applies whether your cluster uses the default capacity or a configured
maximum eCKU. These are the published limits, not a hard cutoff. If your
workload temporarily exceeds a limit, Confluent Cloud might keep serving traffic
instead of immediately rejecting requests or refusing connections.

Depending on cluster load, exceeding limits might result in throttling,
delayed new connections, or unpredictable performance on produce, consume, or
other requests. For more information, see
[Review client application throttles](../monitoring/monitor-performance.md#cloud-client-apps-throttled).

You can lower your maximum eCKU to reduce cluster capacity, but you’re still
responsible for managing your workload within it. If a cluster with a managed
maximum eCKU repeatedly exceeds that reduced capacity, Confluent will
contact you to discuss mitigation. Strategies include reducing your workload
or increasing the maximum eCKU.

Since mid-2026, Confluent enforces stricter limits on
Basic, Standard, Enterprise, and Freight clusters:

- Requests: Enterprise and Freight clusters (effective
  March 2026).
- Connections and connection attempts: Enterprise and
  Freight clusters (effective June 2026).
- Requests, connections, and connection attempts: Basic and
  Standard clusters (effective June 2026).

<a id="cku-details"></a>

## Fixed limits and recommended guidelines

CKUs determine the capacity of your cluster. For a Confluent Cloud cluster, the expected performance for any
given workload is dependent on a variety of dimensions, such as message size and number of partitions.

CKU dimensions fall into two categories:

- Dimensions with a [fixed limit](#fixed-limit) that cannot be exceeded.
- Dimensions with a more flexible [guideline](#guideline) that might be exceeded depending on the overall cluster load.

The recommended guideline for a dimension is calculated for a workload optimized across the dimensions, enabling
high levels of CKU utilization as measured by the [cluster load metric](../monitoring/monitor-performance.md#cloud-cluster-monitor-performance).
You can exceed the recommended guideline for a dimension, and achieve higher performance for that dimension, usually
only if your use of other dimensions is less than the recommended guideline or fixed limit.

Usage patterns across all dimensions affect the workload, and you might not
achieve the suggested guideline for a particular dimension.
For example, if you reach the partition limit, you are unlikely to reach the maximum CKU
throughput guideline.

You should monitor the [cluster load metric](../monitoring/monitor-performance.md#cloud-cluster-monitor-performance) for your cluster
to view how your usage pattern correlates with cluster utilization.

When a cluster’s load metric is high, the cluster might delay new connections, throttle clients, or both,
to keep the cluster available. This throttling registers as non-zero values
for the producer client [produce-throttle-time-max and produce-throttle-time-avg metrics](../client-apps/jmx-monitoring.md#producer-throttling)  and
[consumer client fetch-throttle-time-max and fetch-throttle-time-avg metrics](/platform/current/kafka/monitoring.html#fetch-metrics-kafka).

<a id="fixed-limit"></a>

### Dimensions with fixed limits

The following dimensions have fixed limits that you cannot exceed:

- Storage (pre-replication)
- Partitions (pre-replication)
- Connection attempts
- Kafka REST Produce v3
- Kafka REST Admin v3

<a id="guideline"></a>

### Dimensions with recommended guidelines

These dimensions provide guidelines for capacity planning. The ability to fully use these dimensions
depends on the workload and use of other dimensions.

For more information about measuring load, see
[Dedicated cluster performance](../monitoring/monitor-performance.md#cloud-cluster-monitor-performance). For the maximum bandwidth for
each cloud provider (AWS, Google Cloud, Azure), see
[Benchmark Your Dedicated Apache Kafka Cluster on Confluent Cloud](https://assets.confluent.io/m/2d7c883a8aa6a71d/original/20200501-WP-Benchmark_Your_Dedicated_Apache_Kafka_Cluster_on_Confluent_Cloud.pdf).

The following dimensions come with recommended guidelines:

- Ingress
- Egress
- Total client connections
- Requests

## Partition guidelines

The partition guidelines that follow are based on benchmarking and intended as practical recommendations for planning purposes.
Performance per partition varies depending on your individual configuration, and these benchmarks do not guarantee performance.

Except for Basic clusters, all clusters offer:

- Unlimited storage per partition
- Unlimited storage per partition for compacted topics

Basic clusters offer:

- 5 TB per partition
- 5 TB per partition for compacted topics

Use the table below to compare partition guidelines across cluster types.

| Dimension             | Basic    | Standard   | Enterprise   | Dedicated   | Freight   |
|-----------------------|----------|------------|--------------|-------------|-----------|
| Ingress per partition | ~5 MBps  | ~5 MBps    | ~6 MBps      | ~12 MBps    | ~6 MBps   |
| Egress per partition  | ~15 MBps | ~15 MBps   | ~18 MBps     | ~36 MBps    | ~18 MBps  |

#### NOTE
Ingress figures represent aggregate producer throughput per partition,
and egress figures represent aggregate consumer throughput per partition.

## Migrate from open source Kafka

If you are currently self-managing Kafka, use the following information to help choose which cluster type best suits your use cases. For
information about migrating from open source Kafka to Confluent Cloud, see
the [Migrating from Kafka services to Confluent](https://assets.confluent.io/m/2745775bbd1fa224/original/20240425-EB-Migrating_From_Kafka_To_Confluent.pdf) PDF.

- Ingress: Use [producer outgoing-byte-rate metrics](/platform/current/kafka/monitoring.html#producer-global-request-metrics)
  and [broker kafka.server:type=BrokerTopicMetrics,name=BytesInPerSec metrics](/platform/current/kafka/monitoring.html#kafka-monitoring-metrics-broker)
  to understand your throughput.
- Egress: the [consumer incoming-byte-rate metrics](/platform/current/kafka/monitoring.html#consumer-global-request-metrics)
  and [broker kafka.server:type=BrokerTopicMetrics,name=BytesOutPerSec](/platform/current/kafka/monitoring.html#kafka-monitoring-metrics-broker)
  to understand your throughput.
- Storage (pre-replication): Use the amount of disk space your cluster is using to understand your storage needs.
- Partitions (pre-replication): Use the `kafka.controller:type=KafkaController,name=GlobalPartitionCount` metric to
  understand your partition usage. Find details in the [Broker section](/platform/current/kafka/monitoring.html#kafka-monitoring-metrics-broker).
- Total client connections: Use the [broker kafka.server:type=socket-server-metrics,listener={listener_name},networkProcessor={#},name=connection-count metrics](/platform/current/kafka/monitoring.html#kstypesocketservermetrics)
  to understand how many connections you are using. This value may not have a 1:1 ratio to connections in Confluent Cloud, depending on the
  number of brokers, partitions, and applications in your self-managed cluster.
- Connection attempts: Use the rate of change for the
  [kafka.server:type=socket-server-metrics,listener={listener_name},networkProcessor={#},name=connection-count](/platform/current/kafka/monitoring.html#zk-metrics) metric and
  the Consumer `connection-creation-rate` metric to understand how many new connections you are creating. For details,
  see [Broker Metrics](/platform/current/kafka/monitoring.html#kstypesocketservermetrics)  and [Global Connection Metrics](/platform/current/kafka/monitoring.html#consumer-metric-global-connection-metrics).
- Requests: Use the [broker kafka.network:type=RequestMetrics,name=RequestsPerSec,request!={Fetch,FetchFollower} metrics](/platform/current/kafka/monitoring.html#kafka-monitoring-metrics-broker)
  and [client request-rate metrics](/platform/current/kafka/monitoring.html#kafka-monitoring-metrics-producer)
  to understand your request volume. `Fetch` requests include two types:
  - `FetchConsumer`: A client request to read data
  - `FetchFollower`: An internal replication request between brokers

  This filter excludes `FetchFollower` and the aggregated `Fetch`, but
  retains `FetchConsumer`.

## Related content

- For per-topic settings and limits, see [Manage Kafka Cluster Configuration Settings in Confluent Cloud](broker-config.md#cloud-broker-config)
- For quotas that apply to organizations, environments, clusters, and accounts, see [Service Quotas for Confluent Cloud](../quotas/service-quotas.md#ccloud-resource-limits)
- For performance monitoring your clusters, see [Metrics API](../monitoring/metrics-api.md#metrics-api)
- For costs by dimension, see [Billing Dimensions in Confluent Cloud](../billing/billing-dimensions.md#billing-dimensions)
- For cost estimates, see [Confluent Cost Estimator](https://www.confluent.io/pricing/cost-estimator/)
- For information about migrating from open source Kafka to Confluent Cloud, see the
  [Migrating from Kafka services to Confluent](https://assets.confluent.io/m/2745775bbd1fa224/original/20240425-EB-Migrating_From_Kafka_To_Confluent.pdf) PDF
- For information about the security capabilities of Confluent Cloud, see [Confluent Trust Center](https://confluent.safebase.us/?product=default)
