Any time your services depend on another service there is a cause for concern. You can’t control the performance or the availability of the external service. Further, if the response of the external service is not unique across calls then there may be no real need to call out to it on each request you receive.
In this case, what you want to do is cache the request from the external service and have your service attempt to get the content from the cache. Active cache is a built-in Crafter CMS capability that makes building these sorts of solutions much easier. You tell Active Cache what you want, how to get it, and how often to refresh it in the background. From there on, you simply ask Active cache for whatever the current response is.