Capacity Estimation

Capacity estimation means “how much load a system can handle” before it becomes slow or crashes.
In real systems (like AI, trading platforms, or web apps) engineers estimate users, data, storage, and traffic.

Simple Capacity Estimation Formula

Quick Reference Numbers Engineers Remember

Typical Replication Factors

Peak Traffic Rule

Always multiply average traffic by 3–10×.

Example:

Average traffic = 1000 req/sec

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Peak traffic = 5000–10,000 req/sec

Golden System Design Flow

Example Mini Calculation

Assume:

Users = 1M

Requests/user = 10

Requests/day

1M × 10 = 10M

Requests/sec

10M / 86400 ≈ 115 req/sec

Server capacity

1 server = 200 req/sec

Servers needed

115 / 200 ≈ 1

With redundancy

≈ 5 servers

How to Calculate Storage Requirements in Large-Scale Systems