For real-time notifications, I believe Nats (https://nats.io) or Centrifugo (https://centrifugal.dev) are worth checking out these days. Messages may be delivered to those systems from PostgreSQL over replication protocol through Kafka as an intermediary buffer. Reliable real-time messaging comes with lots of complexities though, like late message delivery, duplicate message delivery. If the system can be built around at most once guarantees – can help to simplify the design dramatically. Depends on the use case of course, often both at least once and at most once should co-exist in one app.
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