# System Limits
This topic specifies maximum sizes and numbers of various SingleStore components. Use the following links to navigate to a section below:
## Cluster-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
| ------------------------------------------------------------ | ---------------------- | ---------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Number of hosts in acluster | None | Workloads that generate significant network traffic between hosts should be limited toclusters with smaller number of hosts. | |
| Number of nodes in acluster(includes leaves and aggregators) | None | Workloads that generate significant network traffic between nodes should be limited toclusters with smaller number of nodes. | |
| Number of databases in acluster | None | | Each database requires memory for transaction buffer and more databases implies greater demand on available memory. |
| Concurrent queries in acluster | None | | Each aggregator will only actually execute a limited number of queries at once (defined by max\_connection\_threads, default 192). Beyond that concurrency, queries will be queued up. |
| Simultaneous client connections | 100,000 per aggregator | | For more information, read about[max\_connections](https://docs.singlestore.com/db/v9.1/reference/configuration-reference/engine-variables/list-of-engine-variables/#non-sync-variables-list.md) |
## Database-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
| -------------------------------------- | ------------------- | ---------------------- | ------------------------------------------------ |
| Number of tables in a database | | | Each table costs some per-table memory overhead. |
| Number of partitions in acluster | None | | |
| Number of database partitions per node | 2414 | | |
## Table-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
| -------------------------------------------------------------------- | ------------------- | ---------------------- | -------------------------------------------------------------------------------------- |
| Number of columns per table | 4096 | | |
| Row size in bytes | 64KB \* | | Limit does not apply to variable-length strings such as VARCHAR, VARBINARY, TEXT, etc. |
| Length of names in characters (applies to table names, column names) | 256 | | |
| Number of indexes per table | 63 | | |
| Number of columns per index | 32 | | |
| Number of tables in a join for each SELECT | 253 | | |
| Number of entries in a`SELECT`projection (target) list | 12800 | | |
| Number of nested sub-select queries using the`UNION`statement | 337 | 40 | Beyond 40 the`UNION`statements are converted to`TABLE`function. |
\* The number of fields that will fit in the 64KB maximum row size is determined by the field types and how rows are laid out in the in-memory rowstore format. In some cases, writes (inserts and updates) to columnstore tables are implemented by storing the newly written rows in a rowstore format before flushing them to the column-oriented format. The row size limit applies to fixed-width data which includes a 4-byte nullability flag for nullable fields. The row size limit does not include the body of variable-width fields, but only the in-row portion, which includes an 8-byte memory location pointer and an optional 4-byte nullability flag. The sum of the in-row data size for all columns cannot exceed 64KB."
## Naming Constraints
| Item | Constraints |
| --------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| General | - Name cannot be blank.
- Name cannot end with a space.
|
| Database names | - Database names can only contain alphanumeric characters and underscores, and cannot start with a digit.
- Maximum length of 64 characters.
|
| Table names | - Table names can contain both alphanumeric and non-alphanumeric characters, but cannot contain the
/ character. - Maximum length of 256 characters. **
|
| Other database objects (stored procedures, views, user-defined functions, user-defined aggregate functions, and table-valued functions) | Maximum length of 256 characters. \*\* |
| User names | - Non-JWT users: Maximum length of 32 characters.
- JWT users: Maximum length of 320 characters.
|
| Role names | No length limit. Cannot contain commas or spaces. |
| Group names | No length limit. Cannot contain commas or spaces. |
\*\* Column aliases are truncated during projection (`SELECT`) to 256 bytes (not characters) which impacts names that use multi-byte characters. The full names are stored in the database and can be queried. Information schema tables can be used to view the full names.
***
Modified at: August 25, 2025
Source: [/db/v9.1/reference/configuration-reference/system-limits/](https://docs.singlestore.com/db/v9.1/reference/configuration-reference/system-limits/)
(An index of the documentation is available at /llms.txt)