Rate Limit Exceed
When a single user makes too many requests to Horizon in a one hour time frame, Horizon returns a rate_limit_exceeded error. By default, Horizon allows 3600 requests per hour – an average of one request per second.
If you are encountering this error, please reduce your request speed. Here are some strategies for doing so:
- For collection endpoints, try specifying larger page sizes.
- Try streaming responses to watch for new data instead of pulling data every time.
- Cache immutable data, such as transaction details, locally
Attributes
As with all errors Horizon returns, rate_limit_exceeded follows the Problem Details for HTTP APIs draft specification guide and thus has the following attributes:
| Description | Type | Attribute |
| The identifier for the error. This is a URL that can be visited in the browser | URL | Type |
| A short title describing the error | String | Title |
| An HTTP status code that maps to the error | Number | Status |
| A more detailed description of the error | String | Detail |
| A token that uniquely identifies this request. Allows server administrators to correlate a client report with server log files | String | Instance |
Rate Limiting
In order to provide service stability, Horizon limits the number of requests a client can perform within a one hour window. By default this is set to 3600 requests per hour—an average of one request per second. Also, while streaming every update of the stream (what happens every time there’s a new ledger) is counted. Ex. if there were 12 new ledgers in a minute, 12 requests will be subtracted from the limit.
Horizon is using GCRA algorithm.
Response headers for rate limiting
Every response from Horizon sets advisory headers to inform clients of their standing with rate limiting system:
| Description | Header |
| The maximum number of requests that the current client can make in one hour | X-RateLimit-Limit |
| The number of remaining requests for the current window | X-RateLimit-Remaining |
| Seconds until a new window starts | X-RateLimit-Reset |
In addition, a Retry-After header will be set when the current client is being throttled.