We're often asked “what is the difference between PubNub and Amazon SNS for latency?” In this blog post, we’ll take a look at both and show you the difference between PubNub and Amazon SNS for publish/subscribe.
Both PubNub and Amazon SNS use a publish/subscribe metaphor for sending and routing data. However, PubNub and Amazon SNS provide different functionalities and solve different business problems; and one actually cannot replace the other. After reading through this blog post, you’ll find that the two technologies are very different, with very different use cases and applications.
PubNub is explicitly designed to deliver data with low latencies (under 0.25 seconds SLA) to end-user devices, including smartphones, tablets, browsers, and laptops. These devices can be behind firewalls, NAT environments, cell towers authorities, and other hard-to-reach network environments; additionally PubNub is providing message caching for retransmission of lost signals over unreliable network environments. PubNub accomplishes this by maintaining an always open socket connection to every device, and using this open socket connection to ‘push’ data at low latencies. PubNub provides over 50 client SDK libraries to make it easy “plug into” PubNub with a simple PubNub Subscribe API call.
Conversely, the main use for Amazon SNS is for server-to-server publish/subscribe use cases, or email & text message end-user notifications. To get a better idea of how Amazon SNS is implemented, check out the common Amazon SNS use cases here. Amazon SNS is also not optimized for in-app real-time notifications. Amazon SNS is more analogous to TIBCO or Tuxedo, which are server-to-server publish/subscribe systems.
Amazon SNS has no way to reach client devices, except via email or SMS notifications. As a result, for applications that rely on low-latency data (such as multiplayer games, chat applications, collaborative apps, etc.) Amazon SNS is not the right solution in for this environment.
The primary way that Amazon SNS sends data to subscribers is via email or HTTP callbacks. Running an HTTP server on mobile, browser, and desktop devices to receive these notifications is impractical, both because of network firewalls and device security reasons.
Amazon SNS latency provides no guarantees, and the vast majority of latencies are measured over 1 second, and often many seconds slower. Again, this is somewhat irrelevant; Amazon SNS is designed for server-to-server (or email/SMS) notifications, where a latency of many seconds is often acceptable and expected.
Because PubNub delivers data via an existing, established open network socket, latencies are under 0.25 seconds from publish to subscribe in the 95% percentile of the subscribed devices. Most humans perceive something as “real-time” if the event is perceived within 0.6 – 0.7 seconds.
Amazon SNS allows for up to 100 “topics” to be created on an account. A “topic” is equivalent to a PubNub channel. Conversely, PubNub supports an unlimited number of PubNub channels. This allows every end-user device to have its own channel for one-to-one connectivity.
Further, PubNub’s support for Multiplexing allows a client device to connect to multiple PubNub channels simultaneously, while continuing to use a single network socket. This allows for a client to simultaneously subscribe to, for example, a “private” channel specifically paired with a single device or set of devices owned by the same person, and a “public” channel that a group or entire population may also subscribed to.
Another use-case for Multiplexing would be a streaming stock price application: Assume you want to stream the stock price changes for 1,000 different equities. Each stock would have it’s own PubNub channel. The end-user device would use PubNub Multiplexing to subscribe only to the PubNub channels associated with the equities they want to track.
Since Amazon SNS does not support Multiplexing, this type of use case is not possible.
PubNub is globally distributed in 14 data centers and growing. All data published into the PubNub Global Cloud is automatically replicated globally, providing both low latency worldwide, as well as unparalleled reliability, even in the event of entire data center failures. PubNub offers up to 99.999% SLA uptime for its Data Stream Network.
Beyond simple publish/subscribe, PubNub offers a collection of real-time building block services for any kind of real-time application. These services are not offered by Amazon SNS or other Amazon services:
Amazon SNS has a variety of interesting uses, mostly related to server-to-server notifications and email/SMS end-user alerts. It was originally developed as a way to orchestrate data between various other Amazon AWS cloud services, and thus is primarily used for server back-end operations and movement of data.
PubNub is designed to make it easy to build real-time apps on mobile, browser, and desktop that scale globally to millions of simultaneous users. Today PubNub is used by over 2,000 organizations globally spanning social, advertising, gaming, telecommunications, and a variety of other markets.
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