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Back-of-envelope calculations

BY Atakan Demircioğlu
Table of Contents

Here are my notes about Back-of-envelope calculations for empowering system design.

Back-of-envelope calculations image 1

Table Of Contents:

What is Back-of-envelope calculations?
 ∘ Useful Calculations (approx)
 ∘ Load Estimates
 ∘ Database Storage estimate
 ∘ Cache Estimate
 ∘ Bandwidth estimates
 ∘ Numbers Everyone Should Know
 ∘ Availability numbers
 ∘ Estimate A Ticket System QPS and storage requirements
 ∘ Some Tips
 ∘ References

What is Back-of-envelope calculations?

Useful Calculations (approx)

1B = 8bits
1KB = 1000B
1MB = 1000KB
1GB = 1000MB

— — — — — — — — — — — — — — —

B: Byte : Ten: 10
K: Kilo : Thousand: 1000 
M: Mega: Million: 1000 0000 
G: Giga: Billion: 1000 000 000 
T: Tera: Trillion: 1000 000 000 000 
P: Peta: Quadrillion: 1000 000 000 000 000

number of zeros after thousands of increments by 3

— — — — — — — — — — — — — — —

char: 1B (8 bits)
char (Unicode): 2B (16 bits)
Short: 2B (16 bits)
Int: 4B (32 bits)
Long: 8B (64 bits)
UUID: 16B

Load Estimates

Database Storage estimate

Cache Estimate

Bandwidth estimates

Numbers Everyone Should Know

Availability numbers

Back-of-envelope calculations image 2

Estimate A Ticket System QPS and storage requirements

Just trying to estimate it, it is not real numbers.

Assumptions:

Estimations:

Estimate QPS (Query Per Second):

Estimate media storage:

Some Tips

References