Code
T4004 live-without-limit
A query that is live is written with rows, and its plan states no limit. A page that watches it is sent every row of the table, and again whenever one of them changes.
Details
A plan that answers one row, a count or groups is bounded by what it is, and needs no limit.
The fix
State a limit: orders.where({ status: 'open' }).limit(50). Or state live: false, which makes the query one that is asked once.