ZynChat

ZynChat: Real-Time Mobile Chat App

Overview

ZynChat is a full-stack mobile chat app focused on reliable real-time messaging between authenticated friends. It combines secure session-based authentication, friend discovery/request flows, Socket.IO-powered chat, typing and presence indicators, and Expo push notifications for offline delivery.

Built as a monorepo: Expo React Native frontend + Bun/Express backend with Prisma and PostgreSQL.

Impact

• Enabled instant one-to-one messaging for accepted friends
• Built complete friend workflow: discover, send request, accept/reject/cancel, chat
• Improved engagement with live presence + typing signals
• Reduced missed messages using push notifications when users are offline
• Maintained smoother UX with unread count sync + read receipt updates across screens

Key Features

• Authentication: Better Auth email/password with protected app routes
• Friend Graph: Relationship-aware discover screen (NONE, FRIEND, REQUEST_SENT, REQUEST_RECEIVED)
• Real-Time Messaging: Socket rooms for private conversations with server-side friend checks
• Presence + Typing: Online/offline status and live typing events
• Unread Management: Conversation-level unread badges + mark-as-read flow
• Push Notifications: New message/friend request pushes, plus action buttons (accept/reject/reply)

Technical Highlights

• Deterministic conversation room IDs from sorted user IDs
• Socket authentication via session cookie in handshake headers
• Business-rule enforcement on backend (no self-message, no non-friend message)
• Optimistic UI updates with React Query + server reconciliation
• Offline-aware push strategy (send push only when receiver is not online)

Future Plans

• Media/file sharing in chat
• Group conversations
• Message reactions and reply threads
• Search and pinned chats
• End-to-end encryption exploration