Latency

• It is the measure of a duration

  • The duration for an action to complete something or produce a result.

  • ie for data to move from one place in the system to another

  • You may think of it as a lag

• most commonly understood latency is the "round trip" network request

  • how long does it take for your client to send a query to your server, and get a response back from the server.

• Low latency is for this action to take as little time as possible

  • Fast lookups means low latency.

  • So finding a value in an array of elements is slower (higher latency, because you need to iterate over each element in the array to find the one you want) than finding a value in a hash-table (lower latency, because you simply look up the data in "constant" time , by using the key. No iteration needed.).

  • reading from memory (low latency) is much faster than reading from a disk (high latency)

• latency is the inverse of speed.

  • You want higher speeds, and you want lower latency.

  • Speed (especially on network calls like via HTTP) is determined also by the distance.

  • ie trade offs: you want to design a system to avoid pinging distant servers, but then storing things in memory may not be feasible for your system.

  • ie websites that show news articles may prefer uptime and availability over loading speed,

  • ie online multiplayer games may require availability and super low latency.

Links

• https://www.infoworld.com/article/3235340/4-sources-of-latency-and-how-to-avoid-them.html

• https://tech.forter.com/9-5-low-latency-decision-as-a-service-design-patterns/

• https://stackoverflow.com/questions/1209803/low-latency-programming

• https://www.youtube.com/watch?v=BD9cRbxWQx8

• https://medium.com/adobetech/engineering-high-throughput-low-latency-machine-learning-services-7d45edac0271

• https://dzone.com/articles/low-latency-java-part-1