There are a lot of questions here, I can’t answer all of them. We’re writing a paper which explains how transactions work, so maybe when that comes out, you could read more about that. But, let me handle the top question here. Feel free to ask any specific questions which might affect how you interact with Dgraph; but as per design related questions, I’d wait for the paper.
No, there’s no way to query a list of pending txns across the cluster. If you lose the start ts somehow, then the best way forward is just to create a new txn and make the changes there. The pending txns automatically get cancelled at some point.