I wouldn&#x27;t say &quot;never&quot;. Let&#x27;s say you have a local file with 1e6 words. The file can be updated at some point. Your service gets a word in a request and needs to return &quot;is this word in the list&quot;.<p>Do you really want to read the file every time at request comes in? No, you&#x27;re going to read it once and store it in an indexed set for quick lookup. You just cached a local data file.<p>It&#x27;s about the benefit vs. not caching. Not about local&#x2F;remote.