Problem
Design the frontend for an Instagram-like app: home feed, Stories tray, post detail, and explore grid.
Discussion areas
- Requirements: infinite feed, Stories (24h expiry), image/video posts, likes, comments, pull-to-refresh, offline viewing of cached feed.
- Media pipeline: responsive images (multiple resolutions), progressive JPEG/AVIF, video HLS adaptive bitrate, blurhash placeholders.
- Stories: separate circular tray component, prefetch next story segment, tap zones (prev/next/pause), progress bars synced to segment duration.
- Feed architecture: normalized store (
postsById,feedIds), cursor pagination, virtualization for scroll performance. - Prefetching: prefetch Stories of followed users on Wi-Fi; idle-time chunk prefetch for explore.
- Real-time: poll or WebSocket for new posts count badge; don't inject mid-scroll.
- Performance: LCP for first post, CLS from reserved media dimensions, code-split routes (camera, DMs).