We want merge request authors to see a real-time, in-app alert the moment someone comments on their work—no refreshing the page. Build the backend that supports this experience. Signed-in users should stay connected to a notifications stream and be identified with a JWT (map each connection to its userId). When a comment is submitted, store it in PostgreSQL and immediately notify the merge request author over that live connection. Send an event named new_comment with { mergeRequestId, commentId, authorName, excerpt }. Provide a simple comments API: POST /v1/merge-requests/:mrId/comments (Bearer JWT) with { text }, responding 201 with the created comment. Use Express (Node.js) and WebSocket.