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Heartbeat

A small periodic message that lets each side notice a connection that has died.

Taught in Chapter 35: Real-time connections.

More from the same chapter

• Connection gateway: A component that holds each client's connection open on a lightweight slot, so one instance carries tens of thousands.
• Handshake: The work of setting up a new connection, which takes a share of an instance's cores before the client is connected.
• Long polling: The client asks, and the server holds the request open until there's news.
• Reconnect storm: Many clients retrying a connection at once after an outage, queueing for the same handshakes.
• WebSocket: One connection that stays open both ways, so the server can send the moment something happens.