Usage limits - ClickHouse Documentation

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.

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.

Dimension	Limit
Databases	1000
Tables	5000
Columns	∼1000 (wide format is preferred to compact)
Partitions	50k
Parts	10k (see `max_parts_in_total` 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

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.

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

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')

Last modified on July 8, 2026

Cloud compatibilityThis guide provides an overview of what to expect functionally and operationally in ClickHouse Cloud.