That&#x27;s a really informative tutorial series.<p>A tip to everyone checking the codebase (JS parts) to learn about building a Trello-like application, there isn&#x27;t any optimistic UI updates in this tutorial app. (eg. after dragging a card to another list, displaying the card at the dragged position before receiving confirmation from the server.)<p>When you add optimistic updates to the mix with real time updates, things get much more complicated. Tracking pending updates, rolling back when something goes wrong, ordering of updates, reconciliation with server when the client is missing some updates etc.<p>I&#x27;m building something similar, and these have been most time consuming parts to build in a reliable way.