# Limits
<a name="SDBLimits"></a>

Following is a table that describes current limits within Amazon SimpleDB.


|  Parameter |  Restriction | 
| --- | --- | 
|  Domain size |  10 GB per domain | 
|  Domain size |  1 billion attributes per domain | 
|  Domain name |  3-255 characters (a-z, A-Z, 0-9, '\$1', '-', and '.') | 
|  Domains per account |  250 | 
|  Attribute name-value pairs per item |  256 | 
|  Attribute name length |  1024 bytes | 
|  Attribute value length |  1024 bytes | 
|  Item name length |  1024 bytes | 
|  Attribute name, attribute value, and item name allowed characters | All UTF-8 characters that are valid in XML documents. Control characters and any sequences that are not valid in XML are returned Base64-encoded. For more information, see [Working with XML-Restricted Characters](InvalidCharacters.md).  | 
|  Attributes per PutAttributes operation | 256 | 
|  Attributes requested per Select operation |  256  | 
| Items per BatchDeleteAttributes operation | 25 | 
| Items per BatchPutAttributes operation | 25 | 
| Maximum items in Select response | 2500 | 
| Maximum query execution time | 5 seconds | 
| Maximum number of unique attributes per Select expression | 20 | 
| Maximum number of comparisons per Select expression | 20 | 
| Maximum response size for Select | 1MB | 
| Exports per domain | 5 in a rolling 24-hour window | 
| Exports per AWS account | 25 in a rolling 24-hour window |