Abstract: A speech interface device is configured to perform natural language understanding (NLU) processing in a manner that optimizes the use of resources on the speech interface device. In an example process, a domain classifier(s) is used to generate domain classifier scores associated with multiple candidate domains, and the candidate domains can then be evaluated, one candidate domain at a time, in accordance with the domain classifier scores (e.g., starting with a highest scoring candidate domain). For each candidate domain undergoing the evaluation, input data is by that domain's NLU model(s), and, as soon as a domain-specific NLU model(s) produces a NLU result with a confidence score that satisfies a threshold confidence score, the evaluation can be stopped for any remaining candidate domains.