Ably

Ably is a hosted real-time messaging service. In a MainSDK app it is a driver behind realtime: your server calls realtime.publish(), and clients listening with realtime.subscribe() get the update. Pick it as an alternative to Pusher when your team already uses Ably.

realtime:
  driver: ably

Before you start

1. Create an Ably app, one per environment.
2. Create an API key for your server with only the capabilities it needs. Clients should get short-lived tokens, never the API key.

Store the API key in your secrets manager.

Configure

realtime:
  driver: ably

How the Ably driver takes its API key is not decided yet; it will be a secret: reference such as secret:ABLY_API_KEY (suggested name).

Use it

import { realtime } from "mainsdk";

await realtime.publish(`order:${order.id}`, { status: "shipped" });

Local development and testing

createTestApp() from @mainsdk/testing runs realtime on its in-memory fake, and chaos.on("realtime", { outage: true }) simulates an outage.

What MainSDK adds on top

• Channel access checked per user and tenant.
• New broadcasts can go out in stages and pause on error spikes.

See Real-time updates.

Limits and notes

• realtime is listed for phase 1, with no spec yet.
• Keep personal data out of messages; send IDs and statuses.

Swap to or from it

realtime:
  driver: pusher   # was ably

Broadcast holds no state in the provider, so it swaps with no migration.

FAQ

Can clients publish through Ably? Not through the catalog calls: clients subscribe and your server broadcasts.

Next

• Real-time updates
• Pusher and Supabase

Open questions