Latency numbers every programmer should know

Latency comparison numbers

Photo by Possessed Photography on Unsplash

Before anything I would like to post a disclaimer that none of these are my measurements and are collected from various different places, GitHub, blogs etc. Within the industry they are commonly known as “napkin estimations”, They are there to serve as a guide for various effects on the ways you choose to communicate.

You can find much more information on my GitHub fork on System Design

Latency Comparison Numbers
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L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy            10,000   ns       10 us
Send 1 KB bytes over 1 Gbps network     10,000   ns       10 us
Read 4 KB randomly from SSD*           150,000   ns      150 us          ~1GB/sec SSD
Read 1 MB sequentially from memory     250,000   ns      250 us
Round trip within same datacenter      500,000   ns      500 us
Read 1 MB sequentially from SSD*     1,000,000   ns    1,000 us    1 ms  ~1GB/sec SSD, 4X memory
HDD seek                            10,000,000   ns   10,000 us   10 ms  20x…