anchor.diff:          AnalysisView analysis)) async {
     final Stopwatch sw = new Stopwatch()..start();
     String cachedPage;
  -  if (backend.uiPackageCache != null) {
  +  final bool isProd = _isProd(request);
  +  if (isProd && backend.uiPackageCache != null) {
       cachedPage =
           await backend.uiPackageCache.getUIPackagePage(packageName, versionName);
     }
  
positive.code:         analysisExtract,
          analysisView);
  
      if (backend.uiPackageCache != null) {
        await backend.uiPackageCache
            .setUIPackagePage(packageName, versionName, cachedPage);
      }
  
negative.code: 
    StaticFile(this.contentType, this.bytes, this.lastModified);
  }
  
  bool _isProd(shelf.Request request) {
    final String host = request.requestedUri.host;
    return host == 'pub.dartlang.org';
  }
  