ThrottlingException when calling IoT SearchIndex

Hi

I have just implemented an api to get the online status for our IoT devices using the SearchIndex operation in AWS IoT. This worked fine during testing, but when it was put into production it failed immediately. I tried manually doing a SearchIndex from the console at the time and got the following error:

> aws iot search-index --index-name "AWS_Things" --query-string "thingName:xxx" --profile yyy

An error occurred (ThrottlingException) when calling the SearchIndex operation (reached max retries: 2): Rate exceeded

How can I find out what the current throttling limit is for this operation?

I found a list of throttling limits in the documentation, but can't see anything that concerns the IoT Index: https://docs.aws.amazon.com/general/latest/gr/iot-core.html#throttling-limits

From our logs found that the API was hit about 90 times per second at the time. We currently have around 430K devices.

We could reduce the load by doing some caching on our side, but without knowing what the limits are, it is difficult to know if that will be sufficient.

Is there perhaps a better way to query the online status of a device?