code: private CompletableFuture<Void> applyConfiguration(Indexed<ConfigurationEntry> entry) {
      for (RaftServiceContext service : raft.getServices()) {
        service.keepAliveSessions(entry.index(), entry.entry().timestamp());
      }
      return CompletableFuture.completedFuture(null);
    }
docs: Applies a configuration entry to the internal state machine.
  <p>
  Configuration entries are applied to internal server state when written to the log. Thus, no significant logic
  needs to take place in the handling of configuration entries. We simply release the previous configuration entry
  since it was overwritten by a more recent committed configuration entry.