Low Latency LiveView

Summary

LiveView sends HTML fragments over a WebSocket connection, allowing Phoenix applications to update the DOM in response to server or user activity. For interactions such as a like button, however, a server round trip can make feedback feel slow: a sub-100ms sequence may be acceptable, while many interactions benefit from responses under 40ms. The post presents client-side state prediction as one remedy, where the browser displays an expected value immediately and later reconciles it with the server. Its preferred “boring” alternative is reducing round-trip time by running application processes near users in multiple cities, connecting Phoenix instances over a private network and enabling clustering. A seven-region Counter deployment is shown with fly regions set and fly scale count 7, while Phoenix.PubSub and Phoenix.Presence handle clustering transparently.

Takeaways

1. 1

   Client-side prediction can display an expected state immediately, then let the server correct it if the prediction was wrong.

2. 2

   The source describes Phoenix clustering as an eight-line configuration using Phoenix.PubSub and Phoenix.Presence to coordinate instances across a network.

3. 3

   The example deploys a LiveView Counter app to seven regions with fly regions set iad lax ams nrt syd sin scl and fly scale count 7.