In 2010, Jeff Dean from Google gave a wonderful talk at Stanford that made him quite famous. In it, he discussed a few numbers that are relevant to computing systems. Then Peter Norvig published those numbers for the first time on the internet.

Time passed, and the numbers changed. Here is a very good interactive web UI of those numbers which roughly tells how much they have changed over the years as a function of time.

This article is not only a compilation of Jeff Dean's estimated data, but rather it brings together all such numbers from different sources. This should help you as a system designer and architect. While designing, you can use these numbers to estimate the amount of resources your system needs.

Rough estimation of latency data for 2019:

  1. L1 cache reference: 1 nanosecond.
  2. L2 cache reference: 4 nanoseconds.
  3. Mutex Lock / Unlock: 17 nanoseconds.
  4. Main memory / RAM reference: 100 nanoseconds.
  5. Compress 1 KB with Zippy (currently called Snappy): 2000 nanoseconds or 2 microseconds.
  6. CPU branch mispredict: 3 nanoseconds.
  7. Solid State Drive (SSD) random read: 16 microseconds.
  8. Disk (Hard drive / magnetic drive) seek: 3 milliseconds.
  9. Read 1,000,000 bytes sequentially from main memory: 4 microseconds.
  10. Read 1,000,000 bytes sequentially from SSD: 62 microseconds.
  11. Read 1,000,000 bytes sequentially from disk: 947 microseconds.
  12. Round trip network request in same data centre : 500 microseconds.
  13. Send 2000 bytes over commodity network: 62 nanoseconds.

Time Taken for payload to travel over TCP:

Here is the amount of time required to transmit various data payloads on typical cell networks around the world assuming no data loss.

RTT — Round Trip Time — Total time taken for a data packet (bunch of data bytes) to travel from sender to receiver and receiver to sender over the network. In short, it’s called Ping time.

  1. Transfer of 1 byte to 13,000 bytes (roughly 13 KB) data takes 1 round trip or 1 RTT. Rough time taken — USA: 150 milliseconds, India: 1200 milliseconds, Brazil: 600 milliseconds.
  2. 13,001 bytes — 39,000 bytes (13 KB to 39 KB) takes 2 RTT. Rough time taken — USA: 300 milliseconds, India: 2400 milliseconds, Brazil: 1200 milliseconds.
  3. 39,001 bytes — 91,000 bytes (39 KB to 91KB) takes 3 RTT. Rough time taken-USA: 450 milliseconds, India: 3600 milliseconds, Brazil: 1800 milliseconds.
  4. 91,001 bytes — 195,000 bytes (91 KB to 195 KB) takes 4 RTT. Rough time taken — USA: 600 milliseconds, India: 4800 milliseconds, Brazil: 2400 milliseconds.

So the greater the response size means more bytes, a longer round trip, more API latency, and ultimately a less user friendly app.

This post will be updated when new or updated numbers are found. Please let me know if you are aware of new numbers.

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