Without Realtime:
App → "Any new messages?" → Server (every 5 seconds)

With Realtime:
Server → "New message!" → App (instantly when it happens)

ALTER TABLE messages REPLICA IDENTITY FULL;

Subscribe to the messages table in Supabase.
When a new message is added, automatically add it to the list.
Don't require a refresh to see new messages.

// Subscribe to changes
let channel = supabase.channel("messages")

channel.on("postgres_changes", filter: .init(
  schema: "public",
  table: "messages",
  event: .all
)) { payload in
  // Handle the change
  switch payload.eventType {
  case .insert:
    // New message added
  case .update:
    // Message updated
  case .delete:
    // Message deleted
  }
}

await channel.subscribe()

Create a chat interface:
- Load existing messages on open
- Subscribe to new messages
- New messages appear instantly at bottom
- Show typing indicators

Build a live activity feed:
- Show recent activities
- Subscribe to activity table
- New activities slide in from top
- Animate new items

Make the todo list collaborative:
- Multiple users can add tasks
- Changes appear instantly for everyone
- Show who made each change
- Handle conflicts gracefully

Add live notifications:
- Subscribe to notifications table
- Show badge count
- Toast notification for new items
- Mark as read when viewed

channel.on("postgres_changes", filter: .init(
  schema: "public",
  table: "messages",
  event: .insert,
  filter: "chat_id=eq.123"
)) { payload in
  // Only messages for chat 123
}

filter: "user_id=eq.\(currentUserId)"

When a new message is inserted:
1. Parse the new message from payload
2. Add to local messages array
3. Scroll to bottom
4. Play notification sound (optional)

When a message is updated:
1. Find the message in local array by ID
2. Replace with updated version
3. UI updates automatically

When a message is deleted:
1. Find the message in local array by ID
2. Remove from array
3. Animate removal

// When view disappears
channel.unsubscribe()

// Or remove all subscriptions
supabase.removeAllChannels()