System Design: Two Independent Systems

You are asked to design two large-scale systems. For each system, provide:

• Scope and key requirements
• External APIs (read/write) and internal service interfaces
• Storage choices and data modeling
• Scalability strategy and high-level architecture
• Consistency model and data flow
• Reliability, availability, and observability plans

Where relevant, estimate traffic/storage, and discuss cost and security trade-offs.

1) Video Sharing Platform (YouTube-like)

Requirements:

• Video upload, validation, and asynchronous transcoding into multiple bitrates and codecs
• Storage tiering (hot/warm/cold), CDN delivery with adaptive streaming (HLS/DASH)
• Metadata and search, user actions (watch, like, comment)
• Recommendations interface (feature and event APIs to interact with a separate recs system)
• Estimate traffic/storage; design ingestion pipeline, thumbnail generation, indexing
• Caching (metadata, watch pages), rate limiting and abuse controls
• Multi-region availability, encryption/DRM, and cost trade-offs

Deliver:

• Architecture, APIs, queues, storage choices
• Consistency choices for user actions and metadata vs search
• Scalability strategy for upload, transcode, playback, and indexing
• Reliability and observability plan

2) Marketplace Catalog System

Requirements:

• Large catalog with categories, attributes, products, and product variants (SKUs)
• Item ingestion (batch/stream), versioning, deduplication, and moderation workflows
• Services for search/browse indexing with localization and incremental updates
• Read/write APIs, caching, and consistency model between the source of truth (SQL/NoSQL) and the search index
• Address schema evolution, multi-tenant isolation, and backfill/reprocessing strategies

Deliver:

• Domain model and storage choices
• Ingestion and moderation flows
• Indexing pipeline and cache strategy
• Consistency, availability, and observability plans