What does scale have to do with it? Pub/sub as an architectural pattern could be equally relevant for your use case whether there are a hundred users in your system or a billion.
And Kafka isn't the only solution for it. There are many lightweight pub/sub and queuing systems which also don't involve needlessly adding abstraction layers and application code into an RDBMS.
>>paxys+(OP)
I think massive scale is the only reason you'd really want to adopt something like Kafka. If you're 10k inserts/s or less then there's no reason not to do everything in a single big relational DB where you get the warm fuzzy feeling of transactions, point in time backups, scalable read replication, etc
>>peterh+62
Yes but then 'enterprise architects' can't put their shiny cloud certifications to use. They need pubsub regardless of the scale because that's what is recommended by big cloud. And of course the companies also don't mind because there is no immediate devops cost for it. The problems like complexity of debugging, lockin won't hit home at the time of design.