I'm not sure what exactly you mean by a timeout ?
Most DSS API calls are asynchronous. This means that if the requested data is not available after 30 seconds they will return an HTTP status 202, and a URL you can poll to find out when the extraction is complete. The DataScope Select REST API conforms to the OASIS OData standards for async. You can find more information in the Key Mechanisms page on Async.
You might find the Best Practices and Limits document useful in this context.
@leor.nussel, There is no need for a timeout; all server failures will be communicated back to your application in the response message; and OS / language libraries will communicate any local network failures. For very long running extraction queries, you can opt for asynchronous delivery of data.
Please see the sample implementation in code examples for DSS in C#, Python and Java language in the downloads tab.