You don't have to cache it for very long, but you get two benefits here: Being able to query the data and search through it ways you simply can't do when making an API call to AWS, and having primarily only one system munching through your API throughput limits. If you've got a large account with a lot of resources and a lot of people or systems that are querying the API frequently, you'll probably have more consistently available data, rather than having systems sitting around doing retries and getting throttled there, on repeat.