In PostgreSQL you can either add yourself as a replica with logical decoding (e.g. PostGraphile supports GraphQL with live queries that way) or do it manually w

In PostgreSQL you can either add yourself as a replica with logical decoding (e.g. PostGraphile supports GraphQL with live queries that way) or do it manually with LISTEN/NOTIFY. On top of that you can use transaction ids or manual transaction serials to get only new rows (but of course note that transactions can be long-running, so you need to either accept potentially unbounded repeated data, or serialize all write transactions on a single serial assignment single-row table, or record the whole set of committed transactions whose data you have processed rather than a single serial number).