Choosing Between Database Subscriptions, Room, and Push

These three features can look similar at first because they all deliver updates quickly. They solve different problems.

Short Version

If you need...	Use
Database changes to appear automatically in the UI	Database Subscriptions
Server-authoritative real-time state with metadata, presence, signals, media, and deltas	Room
Notifications to registered devices, even outside the active app session	Push Notifications

Comparison

Feature	Mental model	Source of truth	Who sends updates?	Reaches only active socket clients?	Best for
Database Subscriptions	"The database changed."	Database rows/documents	Database writes trigger events automatically	Yes	Live feeds, dashboards, document viewers
Room	"The server owns the live session."	Room state + meta + members + signals + media	Clients send actions; server mutates state. Members track presence. Signals relay custom events.	Yes	Multiplayer games, collaboration, conferencing, auctions, voting, online indicators, chat events
Push	"Notify this device."	Registered device tokens in KV + FCM delivery	Server only	No	Mobile/web notifications, re-engagement, background delivery

How to Think About Each One

Database Subscriptions

Use Database Subscriptions when the thing you care about is already stored in the database. The database is the source of truth, and the subscription layer simply delivers change events to clients.

• Think: "show the latest posts, comments, orders, or metrics without polling"
• Good fit: onSnapshot() on a table, query, or document
• Not a fit: arbitrary chat events that are not backed by a row change

Room

Use Room when clients need coordinated real-time interaction beyond simple database change feeds. Room provides five core live surfaces:

• room.state — clients send actions, the server validates and mutates state, and all clients receive deltas
• room.meta — lobby-safe metadata before join, such as mode, capacity, or public labels
• room.members — built-in presence tracking (who is online, typing indicators, cursor positions)
• room.signals — lightweight pub/sub for custom events (chat messages, WebRTC signaling, collaboration cursors)
• room.media (alpha) — audio/video/screen publish, mute, and device state for conferencing UIs

And two operational namespaces round out the client experience:

• room.admin — moderation controls like kick, mute, and role changes
• room.session — connection lifecycle, reconnect, kicked, and error events

Think:

• "the game server decides" → use Room state + actions
• "show a room card before join" → use room.meta
• "who is online right now" → use room.members
• "send a chat message to everyone" → use room.signals
• "track who has their mic on" → use room.media
• "moderate the room from a host client" → use room.admin

Good fit: multiplayer, voting, auctions, collaboration, conferencing, online indicators, chat Not a fit: simple "show latest database rows" — use Database Subscriptions instead

Push Notifications

Use Push when you need delivery to a device, not just to an active socket connection.

• Think: "notify the user even if the app is backgrounded or not currently open"
• Good fit: mentions, order status alerts, reminders, marketing notifications
• Not a fit: low-latency in-app collaboration events between currently connected users

Push is server-initiated and routes through FCM. It is not a WebSocket channel.

Common Confusions

"Is Database Subscriptions really a database feature?"

Yes. It is delivered through WebSocket, but conceptually it is a database change feed. The source of truth is the database.

"Can Room replace Database Subscriptions?"

No. Database Subscriptions deliver changes from database writes automatically. Room is for interactive state that the server manages. If you want to show the latest database rows, use onSnapshot().

"Is Room the same as a chat library?"

No. Room provides the low-level primitives (state, meta, members, signals, media, plus admin / session) that you can use to build chat, but it is not a pre-built chat UI.

"Is Push just another kind of Room signal?"

No. Push targets registered devices through FCM and can reach users outside the current active session. Room signals only reach currently connected WebSocket clients.

Typical Combinations

Chat App

• Database Subscriptions: message list backed by the database
• Room members: online and typing indicators
• Room signals: transient typing or read-receipt events
• Push Notifications: new message alerts when the app is not active

Multiplayer Game

• Room state: authoritative match state and actions
• Room members: lobby-level online indicators
• Push Notifications: match invites or turn reminders outside the live session

Video Conferencing UI

• Room media: track audio/video/screen publish and mute state
• Room signals: WebRTC signaling (offer/answer/ICE candidates)
• Room members: participant list and online status

Decision Checklist

Ask these questions in order:

1. Is the source of truth already in the database? Use Database Subscriptions.
2. Do you need server-owned interactive state, presence, or custom real-time events? Use Room.
3. Must the update reach a device even when the app is not actively connected? Use Push Notifications.