Capacity Estimation Template for System Design

Calculate approximates for the key requirements. You can use below calculation for reference.

Active Users — 2 Billion(B) Daily Active Users(DAU), 3B Monthly Active Users(MAU) — Approximate FB traffic estimate

Read vs Write — 100:1

Queries Per Second —

Reads — (2B DAU)(100Read)/(2460*60) — 2.4M req/sec

Writes — (2B DAU)(1Write)/(2460*60) — 24k req/sec

Storage — (Assuming for 5 years)

No of objects — (2B DAU)(5Y12M*30D) — 3.6 Trillion(T)

Each Object Size — ~ 500 bytes

Total Object size — 3.6T*500 bytes — 1.8 PB

Throughput —

Reads — (2.4M QPS)*(500bytes) — 1200 MB/s

Writes — (24K QPS)*(500bytes) — 12 MB/s

Cache — Following 80–20 rule. 20 % users would use 80% of objs) — (1200 MB/s)(60m60s)*(0.2) — 864 GB per hour

Number of Instances required —

Application Services —