System Design: News Feed for a Food Discovery App

Context

You are designing a news-feed feature for a mobile/web food discovery app where users explore dishes, restaurants, and creator posts. The feed is a scrollable list of items and a tap opens a detailed view. Assume a mix of global and lightly personalized feeds (by cuisine, location, or follows) and mobile clients with intermittent connectivity.

Requirements

Feed and Detail

• Feed items show: title, author, summary, engagement counts (likes, comments, saves), thumbnail.
• Detail view shows: full description, images, comments (threaded or flat), related items.
• Infinite scroll on feed and comments.
• Rank by a blend of recency and engagement.
• Basic search and filter (e.g., keywords, cuisine tags, location radius, author).

Data and Operations

• CRUD for posts and comments, reactions (like/save) on posts and comments.
• Data model and storage for posts, comments, reactions, counters, and related items.

Interfaces

• Read/Write APIs with pagination (cursor-based preferred), idempotency for writes.

Architecture & Platform

• End-to-end request path: edge/CDN, API gateway, stateless app tier, caches, DB, background jobs, queues/streams, data processing/indexing.
• Caching, indexing, and denormalization for fast reads.
• Scalability: partitioning/sharding, rate limiting, backpressure, horizontal scaling.
• Consistency choices (strong vs eventual) and idempotency.
• Error handling and retries (client/server), DLQs.
• Observability: logging, metrics, tracing, SLOs.
• Performance optimizations for p95 latency and cost.