Overview of system design for ranking products by category on Amazon

1. Methodology
1. 5 Step Process
1.1. Use cases, assumptions, constraints
1.2. Back of envelope calculations
1.3. Design core components
1.4. High level design
1.5. Scale the design

2. Amazon Recently Viewed Items
Step 1a: Use Cases
● Functional requirements (use cases)
○ Service calculates the past week's most popular products
by category
○ User views recently viewed items
● Nonfunctional requirements
○ High availability

3. Amazon Recently Viewed Items
Step 1b: Assumptions / Constraints
● Uneven traffic
● 1 million products
● 100 categories
● 1 billion write transactions/month
● 50 billion write transactions/month
○ 50:1 read-write (read heavy)

4. Amazon Recently Viewed Items
Step 2a: Back of envelope calculations
● Database design
○ Users table: ~50 bytes
○ Products table: ~50 bytes
○ Categories table: ~50 bytes
○ Transactions table: ~50 bytes

5. Amazon Recently Viewed Items
Step 2b: Back of envelope calculations
● Daily Traffic
○ 1 billion write transactions/month
■ ~380 write/s
○ 50 billion write transactions/month
■ ~19,000 read/s
● Storage
○ Size per transaction per month
■ 50 GB writes/mo = 50 bytes * 1 billion writes/month
■ 250 GB reads/mo = 50 bytes * 50 billion reads/month

6. Amazon Recently Viewed Items
Step 3: Design core components
● Use case#1: Service for popular products by category
○ Write API gathers raw rank data
○ Rank service using MapReduce for data
● Use case #2: Users view latest products
○ Read API views data in SQL

7. Amazon Recently Viewed Items
Step 4: High Level Design

8. Amazon Recently Viewed Items
Step 5: Scale Design
● 250 billion read transactions/month (read heavy)