Currently, up(MessageBatch batch) creates a list of all messages plus their seqnos and calls Table.add(List). This temporary list creation causes memory allocation; to avoid it, we can create a method Table.add(MessageBatch) and pass the batch directly to the table. This saves 1 memory allocation on each up(MessageBatch) call.
The method to add a MessageBatch must have a parameter function which extracts the seqno given a Message.