Tutorial

Realtime

What a channel is, how clients connect, and where to go next.

Checked 2026-10-07

A Realtime Channel is an ordered stream of messages in one environment. Your server publishes to it with a key; every connected browser, app or device receives each message as it is appended, and a client that drops resumes from the last message it saw. Realtime is part of Sylphx Events: there is nothing to deploy, one key in your project is enough.

#What a channel gives you

• Ordered history. Every message gets a sequence (from 1, gap-free) and a cursor, and is kept for the channel's spec.history_retention: 24 hours by default, at most 7 days.
• Resume, not replay by hand. A client that reconnects sends its last cursor and receives exactly the messages after it. Server-Sent Events clients do this on their own through Last-Event-ID.
• Two transports. status.connect_uri is a WebSocket that pushes messages and carries presence; status.stream_uri is Server-Sent Events, for clients that only read.
• Clients hold no secret. Your server mints a short-lived token (rtt_…, at most an hour) for one channel, and the client connects with it. A channel with spec.publishable_ok also admits a publishable key.
• Presence. A token that names a client id puts that client in the channel's members while it is connected, and the channel carries presence.enter and presence.leave messages.
• Idempotent publish. A publish retried with the same Idempotency-Key returns the first message instead of appending a second.

#Names and ids

Channel

orgs/{org}/projects/{project}/envs/{env}/realtime_channels/{realtime_channel}

Channel id

rtc_<cell><ulid>

Message

…/realtime_channels/{realtime_channel}/realtime_messages/{realtime_message}

Message id

rtm_<cell><ulid>

Subscribe token

rtt_…

#The scopes

• events:write — creating, changing and deleting a channel.
• events:publish — publishing a message, and minting a subscribe token.
• events:read — reading channels, their message history and their members.
• events:realtime:subscribe — connecting to a channel's stream with a key instead of a token. A publishable key may hold it, for channels that allow publishable keys. Keys and scopes covers the two kinds of key.