Kakao Implements Real-Time Features for 'Alex Comments' with 600K DAU; Reveals Kafka, NiFi, and Redis-Based Architecture

The Kakao Interaction Platform team designed an architecture independent of existing systems to introduce real-time features to the 'Alex Comments' service, which exceeds 600,000 DAU and handles thousands of requests per second. To guarantee real-time performance, WebSockets were chosen over polling, and Kafka was selected as the message broker to ensure integration with the existing comment system. Apache NiFi was adopted as the message processing processor due to its suitability for distributed data processing, allowing for intuitive design and control of data flows. The message flow of the completed architecture is as follows: when a user performs a comment creation, upvote, or downvote action, the existing system loads events into Kafka, and the NiFi-based processor subscribes to them, processes them, and publishes them to a Redis channel. Subsequently, the WebSocket server subscribes to the Redis channel to deliver real-time updates to clients.