Short answer

Supabase Realtime for anything where your source of truth is already a Supabase table. Socket.io for peer-to-peer, chat rooms, ephemeral signals that do not belong in a table.

I have used both on shipped apps. The choice is simpler than the internet makes it sound.

Supabase Realtime strengths

• Zero extra infrastructure. If you already use Supabase for data, you already have Realtime.
• Authorization piggybacks on RLS. Row-level policies apply to the realtime stream automatically.
• postgres_changes gives you insert/update/delete events from a table without writing a publisher.
• Presence built in for "who is online" features.
• Reconnect is handled. Tokens are refreshed. You do not wire any of it.

Supabase Realtime weaknesses

• Throughput cap. You are not going to run a 100k concurrent-player game on it.
• Your events are tied to database rows. If your domain is "transient signal, no row", you are working against the grain.
• Latency is fine for mobile UX but it is not the lowest you can get.

Socket.io strengths

• True arbitrary events. Emit anything from anywhere. No schema constraint.
• Rooms and namespaces are first-class.
• Mature ecosystem with React Native client.
• You control the server, so you control performance.

Socket.io weaknesses

• You run the server. That is a real operational cost — scaling, sticky sessions, reconnects.
• Auth is yours to implement. No RLS.
• Token refresh on long-lived connections is a problem you own.
• Native RN WebSocket reconnection is finicky on Android when the app backgrounds.

Real-world performance I measured

A delivery app with ~80 drivers online, each pushing a location every 10 seconds, and ~500 customers subscribing to their assigned driver:

• Supabase Realtime: server-to-client latency 180–350ms. One reconnect per hour on average.
• Socket.io (self-hosted on Oracle Cloud): 90–150ms. Similar reconnect frequency.

The Socket.io setup was faster but took an extra two weekends to run reliably. Not worth it for the product I was building.

When I pick Socket.io

• Multi-user live collaboration (cursors, whiteboards).
• Live sports or games.
• Anything where I need event types that are not rows.

When I pick Supabase Realtime

• Any mobile app where the data already lives in Supabase.
• Order tracking, chat messages that are just rows, presence.
• Anything small-to-medium scale.

What AI App Factory ships

Supabase Realtime wired in by default, with the hooks I use (useRealtimeTable, useChannelPresence). If you need Socket.io later, the backend has a NestJS module you can enable — it is not in the default build.

See pricing