Part 2: How I Calculate Capacity for Systems Design – 2
Capacity Estimation in System Design
Capacity estimation is essential to ensure that a system can handle its expected load and perform efficiently. It involves calculating the resources needed for processing/traffic handling, storage, and network bandwidth.
Key Rules for System Design Estimation Calculations
Rounding Approximations
Simplify calculations by rounding to more manageable numbers.
Example: Instead of calculating for 86,400 seconds in a day, use 100,000 (100K) seconds to simplify.
Powers of 2 and 10
Familiarize yourself with powers of 2 and 10 for quick estimations.
Example values for powers of 2: 2, 4, 8, 16, 32, 64, etc.
Example values for powers of 10:
(10^1 = 10)
(10^2 = 100)
(10^3 = 1,000)
(10^6 = 1,000,000) (1 million)
(10^9 = 1,000,000,000) (1 billion)
(10^{12} = 1,000,000,000,000) (1 trillion)
Metric System
Use metric system units for large numbers:
1 million = (10^6)
1 billion = (10^9)
1 trillion = (10^{12})
Storage Capacity
Understand common storage units:
1 KB = (10^3) bytes
1 MB = (10^6) bytes
1 GB = (10^9) bytes
1 TB = (10^{12}) bytes
1 PB = (10^{15}) bytes
Storage Assumption
Storage Assumption
Size
Single Char
2 bytes
Long/Double
8 bytes
Image
200 KB
Video
2 MB
Key Metrics to Memorize
1 million requests per day ≈ 12 requests/second
1 million requests per minute ≈ 700 requests/second
1 million requests per hour ≈ 4,200 requests/minute
Latency Numbers
Familiarize yourself with common latency benchmarks to make informed decisions during system design.
Note: Google for a table of latency benchmarks for more details.
Table for Powers of 2 and 10
Power of 2
Value
Power of 10
Value
(2^1)
2
(10^1)
10
(2^2)
4
(10^2)
100
(2^3)
8
(10^3)
1,000
(2^4)
16
(10^6)
1,000,000
(2^5)
32
(10^9)
1,000,000,000
(2^6)
64
(10^{12})
1,000,000,000,000
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