How much is OpenAI able to cache query results? There's a major difference in speed on some queries and in my experience the queries on which it is slow to resp

How much is OpenAI able to cache query results? There's a major difference in speed on some queries and in my experience the queries on which it is slow to respond are almost always very unusual and difficult to answer queries. I feel that caching responses would be very difficult and the answers chatgpt gives vary quite a bit for the same query, but it also doesn't make any sense to me why query response times should differ so significantly based on query difficulty if all its doing is inference in a language model.