Live Comment System Design

Feed: Real-Time Live Commenting Platform

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High-Level Design

The Live Comment service carries out the following operations at a high level:

• The gateway server distributes live comments to the clients via server-sent events (SSE)

• Clients subscribe to a live video on the gateway server using Hypertext Transfer Protocol (HTTP)

• The gateway server maintains an in-memory subscription store to keep track of viewership associations

• The gateway server subscribes to a live video on the endpoint store

• The endpoint store manages the list of gateway servers subscribed to a specific live video

• Heartbeat signals or time to live (TTL) on keys in the subscription store can be used to handle inactive SSE connections

• When a live video ends, it triggers an update in the endpoint store

• The dispatcher broadcasts live comments to the dispatcher in peer data centers

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