It's not my area, but it seems like if your application is deeply dependent on an API it might be a good idea to directly reference the IP address? Over 1000s of requests, wouldn't that save time?
It would be slightly faster. However, if you ever had to change your server's IP address (for example, because you had to move to a new hosting provider) you'd be utterly screwed.
That scheme assumes that the service is hosted at a stable IP address, which in almost all cases is not a valid assumption.
Not my area either but I think dns queries are cached locally for a certain amount of time so dns lookup for 1000s of requests shouldn't give too much overhead
Edit: yeah and also what the other guys said about not relying on the ip being the same forever