Latency Trumps All

Chris Saari (Yahoo!)
Focus on Cloud Computing
Location: 2010 Level:
Average rating: ***..
(3.22, 9 ratings)

Dealing with latency is what keeps many engineers awake at night and drives much of the real time web revolution as we know it today. From Twitter’s up to the moment updates, to instant messaging, to Google serving a search result in the blink of an eye dealing with latency is the key to keeping the web, and your own computer, running quickly. Learn how to conquer latency for building fantastic products by looking at examples from around the industry.

If you look at most of Google’s architecture, tools and systems from a high enough level you realize that it is all a designed around the concerns of latency (and expected failure, but this talk is about latency). Latency in networks, in disk reads and writes, from main memory to CPU, you name it. A handy chart that keeps me awake at night:

  • Relative Data Access Latencies, Fastest to Slowest
  • CPU Registers (1)
  • L1 Cache (1-2)
  • L2 Cache (6-10)
  • Main memory (25-50)
  • —- don’t cross this line, don’t go off mother board! —-
  • Hard drive (1e7)
  • LAN (1e7-1e8)
  • WAN (1e9-2e9)

That particular set of relative data access speeds and the speed of light itself determine exactly how Google, Yahoo, Facebook, Twitter and everyone else must design their software and systems in order to achieve maximum performance on a single machine, and across many machine services and networks.

Looking at the world through the lens of latency we’ll cover Facebook’s memcached changes, Facebook Cassandra, Google’s search, Google File System and BigTable architectures, Intel’s new (AMD’s old) memory access architecture and why solid state disks are the future (hint: they reduce data access latency).

Hopefully you’ll come away from this talk with a better sense of the constraints of physics in computing, and the solutions engineers are working on to keep the web and your own computers from hurrying up and waiting.

Photo of Chris Saari

Chris Saari


More than 14 years working as an engineer and leader in Silicon Valley at companies including Apple, PointCast, Netscape / Mozilla, Macromedia and Yahoo on products including Mozilla/Netscape, Dreamweaver, Flex Builder 2 and Yahoo! Messenger.

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