Requirements

• Functional requirements
• Operational requirements
  • Availability
  • Performance
  • Latency
  • Legal & Compliance & privacy
  • Maintenance (data lifecycle)
  • Capacity
  • Security
  • Geo
• Logging and Metrics

Back of the envelope estimations

• QPS (read) & (Write)
• Storage estimations
• Memory estimations

High level design

• X-tier design
• Objects
• State diagrams
• API for those objects
• Roughly the services
• DB solutions

Detailed design

• Walk thru functional requirements
• Scalability & Performance & Availability
  • Vertical
  • Horizontal scaling
  • CDN
  • Load balancers
  • Async communication
  • Data centers
  • Caching
  • Database
    • Sharding
    • Replication
• Logging & Metics