What is Latency and Why Does it Matter?

3 min readChandler Mayo on Jan 30, 2019
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A simple explaination of what latency is, why latency matters, and why you should care about it.

PubNub ensures global latency of under 250 milliseconds worldwide, with a goal of delivering messages within 100 milliseconds. For us, latency is critical for a quality experience on our platform and for our clients. But taking a step back, what is latency? Why does latency matter and why should you care about latency?

Latency is Delay

Latency is the delay between initiating an action (publishing a message) and the effect of that action (receiving a message). Latency is usually measured in milliseconds (ms). You may see latency referred to as the ping rate in an Internet speed test. In a network, latency is introduced in the processing and transmission of data.

What is the definition of network latency?

Network latency refers to any delay of data transmission in a network.  zero-latency-icon PubNub is optimized to reduce latency introduced in the processing and replication of messages sent on the PubNub Data Stream Network. This optimization, a result approaching a decade of fine-tuning, gives PubNub's clients an edge when they rely on our network for global real-time transmission of their messages.  PubNub’s core Data Stream Network is extremely fast. Routing a message through the PubNub network takes as little as 4-9 milliseconds, often resulting in an end-to-end transmission of 30-40ms for clients on a broadband connection. A majority of any latency experienced will be from the client transmission of messages to and from a PubNub PoP (point-of-presence, A.K.A a data center). There are three factors that will affect your messages between your clients and our PoPs: connection type, distance, and congestion.

Connection Type

satelliteHow your clients are connected to the Internet will affect your latency to our PoPs. Satellite internet is usually the worst type of Internet connection to use with latency sensitive applications. Data has to be sent wirelessly to an orbiting geostationary satellite 22,300 miles above Earth's equator and then back again, sometimes multiple times, before reaching one of our PoPs. The transmission, while happening at light speed, still takes a lot of time because of the distance and atmospheric noise. Latency/ping on a satellite connection can be 500ms or more. The best type of connection for latency-sensitive applications is fiber optic, which can have a latency as low as 1-2ms. Most home cable connections advertise a latency of 10-100ms.


Latency will increase the further your clients are from a PubNub PoP. We offer 15 PoPs strategically deployed across Western and Eastern Europe, North and South America, and throughout Asia, to eliminate as much distance between your clients and PubNub as possible.


Warning Congestion Congestion is when a network is carrying more data than it can handle. If a network is overloaded, it doesn't matter how fast the data is traveling because it will either be delayed or lost entirely when it reaches the congestion. You'll see network congestion when too many clients are sharing a network that doesn't have enough bandwidth, like a highway with too many cars.

Why Does Latency Matter and Why Should You Care About Latency?

Latency is Money Reduced latency usually translates to a more efficient application and a better user experience. Even in applications that don't need to be real-time, a user will become frustrated if something isn't fast enough to be considered instant. In the gaming industry, latency isn't just annoying, it drastically impacts user experience and the perceived quality of a game. In the on-demand economy, a big part of the user experience relies on instantaneous updates and confirmations. Simply put, users will abandon your application if they have to wait for it. Eliminating latency in your application can be worth millions of dollars in gained or lost profits.

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