Rental Search Ranking System Design

4. Calculation & estimation

Assumptions

• 100 million monthly active users
• On average, users book rental homes 5 times per year. Users see about 30 rentals from the search result before booking.
• There are 5 * 30 * ${10 ^ 8}$ or 15 billion observations/samples per year or 1.25 billion samples per month.

Data size

• Assume there are hundreds of features per sample. For the sake of simplicity, each row takes 500 bytes to store.
• Total data size: 500 * 1.25 * ${10^9}$ = 625 * ${10^9}$ bytes = 625 GB. To save costs, we can keep the last 6 months or 1 year of data in the data lake, and archive old data in cold storage.

Scale

• Support 150 million users

5. High-level design