# Usage Limitations

UAPIGateway has certain limitations on the use of resources, including the number of group/API definitions, URI length, number of parameter mappings, number of custom domain names, number of back-end definitions, etc.
* For resource definition restrictions, if the quota is exceeded, an error will be reported when creating the number in the console
* For resource usage restrictions, such as QPS, Header size, etc.; errors will be returned by the gateway during use.

| Category | Limitation | Can be Increased|
| ---- | ----| -----|
|Number of API groups | 50 | Yes|
|Number of APIs in each API group|50|Yes|
|Number of custom domain names of the API group|50|Yes|
|Number of back-end services of the API|5|Yes|
|Number of custom error codes of the API|50|No|
|Number of parameters of the API parameter mapping|50|No|
|Number of HTTP Headers for calculating signatures|10|No|
|Request URL length limitation|4KB|No|
|Request HTTP Header size limitation|4KB|No|
|Request HTTP Body size limitation|4MB|No|
|Response HTTP Header size limitation|4KB|No|
|Response HTTP Body size limitation|8MB|No|
|QPS of each API group|1000|No|