docs: private void sendMessages(final List<MessageEnvelope> msgEnvelopes) {
          try {
              boolean success=BackendOperation.execute(new BackendOperation.Transactional<Boolean>() {
                  @Override
                  public Boolean call(StoreTransaction txh) throws BackendException {
                      ListMultimap<StaticBuffer,Entry> mutations = ArrayListMultimap.create();
                      for (MessageEnvelope env : msgEnvelopes) {
                          mutations.put(env.key,env.entry);
                          long ts = env.entry.getColumn().getLong(0);
                          log.debug("Preparing to write {} to storage with column/timestamp {}", env, times.getTime(ts));
                      }
  
                      Map<StaticBuffer,KCVMutation> muts = new HashMap<StaticBuffer, KCVMutation>(mutations.keySet().size());
                      for (StaticBuffer key : mutations.keySet()) {
                          muts.put(key,new KCVMutation(mutations.get(key),KeyColumnValueStore.NO_DELETIONS));
                          log.debug("Built mutation on key {} with {} additions", key, mutations.get(key).size());
                      }
                      manager.storeManager.mutateMany(ImmutableMap.of(store.getName(),muts),txh);
                      log.debug("Wrote {} total envelopes with operation timestamp {}", msgEnvelopes.size(), txh.getConfiguration().getCommitTime());
                      return Boolean.TRUE;
                  }
                  @Override
                  public String toString() {
                      return "messageSending";
                  }
              },this, times, maxWriteTime);
              Preconditions.checkState(success);
              log.debug("Wrote {} messages to backend",msgEnvelopes.size());
              for (MessageEnvelope msgEnvelope : msgEnvelopes)
                  msgEnvelope.message.delivered();
          } catch (TitanException e) {
              for (MessageEnvelope msgEnvelope : msgEnvelopes)
                  msgEnvelope.message.failed(e);
              throw e;
          }
      }