Usage limits
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.
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) |
| 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 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.
