We are using react-flow for generating node/showing nodes on the frontend, so it was getting very hard for us to manage the nodes and edges.
So we had to hit our heads into it so much.
Also another thing was integrating payment processor, we got the access of it few days ago, and their docs was not up to the mark so we had to do so much of testing to get it working. and most hard part was setting up webhooks to listen payments.
and we were getting many errors of different stuff after deploying, so it was fun to solve.