Postgres LISTEN/NOTIFY actually scales

# Summary Postgres LISTEN/NOTIFY has a reputation for poor scalability due to a global exclusive lock taken during NOTIFY operations, but Peter Kraft demonstrates it can actually scale effectively. By optimizing their implementation, the team achieved 60K writes per second with millisecond-latency on a single Postgres server, compared to the initial 2.9K writes per second, making LISTEN/NOTIFY a viable solution for low-latency durable notifications and pub/sub use cases.