We needed to implement continuous queries in our application code. (It's actually hard to do it right in Postgresql so it's very limited) https://github.com/buremba/rakam/wiki/Postgresql-Backend#con... Since stream processing and real-time analytics are quite hot topics nowadays, I think real-time databases will get much more attention in a near future.
Sorry for the late response. HN just sent me notification mail.
The documentation states it as "by default". It's required to change wal settings in config file and write a custom logical decoding output plugin in order to take advantage of that feature.
Currently, PaaS provisers such as RDS and Heroku Postgres don't support and it would not be easy to setup it manually. AFAIK, that feature is intended to be to used for backups.
