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 default values of these guardrails are listed below. Unless specified otherwise, these guardrails are on the service level.

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 support 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	150 GB
Services per organization	20 (soft)
Replicas per service	20 (soft)
Replicas per warehouse	50 (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 rows is split into 1M-row blocks

For warehouse replica and scaling limits, see warehouses. The values above are default guardrails. The limit enforced for a specific service may be higher than the value shown here, as larger services are configured with more headroom. The actual limit that applies to your service is included in the warning you receive as you approach it. For services already exceeding the above usage limits, table/database limits are set at the service’s current table/database count plus 25%.

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.

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 August 5, 2026