> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Usage limits

> Describes the recommended usage limits in ClickHouse Cloud

While ClickHouse is known for its speed and reliability, optimal performance is
achieved within certain operating parameters. For example, having too many tables,
databases, or parts can negatively impact performance. To prevent this, ClickHouse
Cloud enforces limits across several operational dimensions.
The details of these guardrails are listed below, which show default values.

<Tip>
  If you've run up against one of these guardrails, it's possible that you're
  implementing your use case in an unoptimized way. Contact our support team and
  we will gladly help you refine your use case to avoid exceeding the guardrails
  or look together at how we can increase them in a controlled manner.
</Tip>

| Dimension                     | Limit                                                                                                         |
| ----------------------------- | ------------------------------------------------------------------------------------------------------------- |
| **Databases**                 | 1000                                                                                                          |
| **Tables**                    | 5000                                                                                                          |
| **Columns**                   | ∼1000 (wide format is preferred to compact)                                                                   |
| **Partitions**                | 50k                                                                                                           |
| **Parts**                     | 10k (see [`max_parts_in_total`](/docs/products/cloud/guides/cloud-compatibility#max_parts_in_total-10000) setting) |
| **Part size**                 | 150gb                                                                                                         |
| **Services per organization** | 20 (soft)                                                                                                     |
| **Services per warehouse**    | 5 (soft)                                                                                                      |
| **Replicas per service**      | 20 (soft)                                                                                                     |
| **Low cardinality**           | 10k or less                                                                                                   |
| **Primary keys in a table**   | 4-5 that sufficiently filter down the data                                                                    |
| **Query concurrency**         | 1000 (per replica)                                                                                            |
| **Batch ingest**              | anything > 1M will be split by the system in 1M row blocks                                                    |

<Note>
  For Single Replica Services, the maximum number of databases is restricted to
  100, and the maximum number of tables is restricted to 500. In addition, storage
  for Basic Tier Services is limited to 1 TB.
</Note>

<Note>
  For services already exceeding the above usage limits, table/database limits are set at the service's current table/database count plus 25%.
</Note>

Your service's specific warn and throw limits can be verified by querying system.server\_settings. For example,

```
SELECT * 
FROM system.server_settings 
WHERE name IN ('max_table_num_to_warn', 'max_table_num_to_throw', 'max_database_num_to_warn', 'max_database_num_to_throw')
```