Can I check how long does it take to get a response when I call 200 instruments in 1 API call with 30 ContentFieldNames in my request when calling the Composite Request API? Also, how long does it take before the call times out?
There is no specific time expectation on a DSS REST API request processing. Depends on the request itself, but also depends on the current service load, even network bandwidth and load.
The approach is designed to be asynchronous to deal with various request sizes, and system loads.
In brief, if if the request can complete in 30 sec, the response code will be 200, the result is ready to retrieve. Otherwise, the response code will be 202, and includes extraction id and the API requestor should check on the status of the request by extraction id periodically, till status becomes 200, and then download the result.
You will find more details and step-by-step on a specific request, including Authentication part, in DSS Tutorials section, see REST API Tutorial 8: On Demand composite extraction on processing composite data and REST API Tutorial 2: On Demand End of Day Extraction on the two approaches and the timeout handling.
Hope this helps?