[alecgibson]

At the moment, a subscribed query with more than one channel defaults pollInterval to 1000, so it re-runs against the database every second for as long as it's subscribed, even when nothing has changed. At Reedsy, that was ~2/3 of all our ShareDB requests.

Nothing asks for that interval. It arrived with multi-channel queries in #587, where review only suggested a pollDebounce default to batch polls. The interval catches changes that don't publish an op on any of the query's channels, which depends on how an app picks its channels, not how many there are, and a query on one channel has never had it.

This is a BREAKING CHANGE, though apps that already set pollInterval are unaffected. The pollDebounce default is unchanged, and this middleware, registered after the one that sets context.channels, restores the old interval:

backend.use('query', (context, next) => {
  if (context.channels.length > 1) context.options.pollInterval = 1000
  next()
})

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

[Copilot]

🟢 Approval recommended

No active review issues were identified for the change removing automatic polling from multi-channel query subscriptions.

No open issues 🎉

What changed in this PR

This PR removes automatic one-second database polling for multi-channel query subscriptions, reducing unnecessary database load. This is a breaking default change; explicitly configured polling intervals and the existing debounce behavior remain unchanged.

Changes:

• Default pollInterval to zero regardless of channel count.
• Add a regression test for timer-free subscriptions and remove redundant interval overrides.
• Document polling defaults and when an explicit interval is useful.

File	Description
test/​client/​query-subscribe.js	Adds timer-polling regression coverage and removes redundant overrides.
lib/​query-emitter.js	Removes the multi-channel polling interval default.
lib/​backend.js	Documents the purpose of pollInterval.
docs/​middleware/​actions.md	Clarifies interval and debounce defaults.

_{Review effort: Balanced}

[coveralls]

coverage: 98.049%. remained the same — no-multi-channel-poll-interval into main

[dawidreedsy]

I really do not remember why did the polling 1000, but it seems fine without it.