docs: private void updateDelta(Applications delta) {
          int deltaCount = 0;
          for (Application app : delta.getRegisteredApplications()) {
              for (InstanceInfo instance : app.getInstances()) {
                  ++deltaCount;
                  if (ActionType.ADDED.equals(instance.getActionType())) {
                      Application existingApp = getApplications()
                              .getRegisteredApplications(instance.getAppName());
                      if (existingApp == null) {
                          getApplications().addApplication(app);
                      }
                      logger.debug("Added instance {} to the existing apps ",
                              instance.getId());
                      getApplications().getRegisteredApplications(
                              instance.getAppName()).addInstance(instance);
                  } else if (ActionType.MODIFIED.equals(instance.getActionType())) {
                      Application existingApp = getApplications()
                              .getRegisteredApplications(instance.getAppName());
                      if (existingApp == null) {
                          getApplications().addApplication(app);
                      }
                      logger.debug("Modified instance {} to the existing apps ",
                              instance.getId());
  
                      getApplications().getRegisteredApplications(
                              instance.getAppName()).addInstance(instance);
  
                  } else if (ActionType.DELETED.equals(instance.getActionType())) {
                      Application existingApp = getApplications()
                              .getRegisteredApplications(instance.getAppName());
                      if (existingApp == null) {
                          getApplications().addApplication(app);
                      }
                      logger.debug("Deleted instance {} to the existing apps ",
                              instance.getId());
                      getApplications().getRegisteredApplications(
                              instance.getAppName()).removeInstance(instance);
                  }
              }
          }
          logger.debug(
                  "The total number of instances fetched by the delta processor : {}",
                  deltaCount);
  
      }