# Send / sync examples

## Persist then enqueue then ACK

```go
msg.ID, err = idgen.NextMsgID()
if err != nil { return nil, err }
if err := repo.Create(ctx, msg); err != nil { return nil, err }
if err := convRepo.UpdateLastMsg(ctx, msg.ConversationID, msg.ID, now); err != nil { return nil, err }
if err := deliver.Push(ctx, &deliver.Job{MsgID: msg.ID, ExcludeDevice: req.DeviceID}); err != nil {
    return nil, err // no SEND_ACK
}
return &SendResponse{MsgID: msg.ID, ClientMsgID: req.ClientMsgID, ServerTimeMS: now}, nil
```

## EventLoop submit

```go
if frame.Command == protocol.CmdHeartbeat {
    return writeHeartbeat(c, frame)
}
_ = pool.Submit(ctx, func() { router.Dispatch(ctx, frame) })
```

## Sync

```sql
SELECT * FROM messages
 WHERE conversation_id = ? AND id > ?
 ORDER BY id ASC LIMIT 200;
```

Inbox sync reads Redis ZSET by `dialog_score`, then mailbox events by `mailbox_seq`.