You do not need a database. It is trivial (and correct) to create a ~'<x>-status' topic. In the forward arc you are reliably propagating job requests (acked). In the backflow the processing status of job is posted for anyone interested. You can even propagate retries, etc. It is an MQ and RabbitMQ shines in defining complex dispatch toplogies.
Yeah but they already have a database, so it's not like they're adding a database to the system. And (as the article says) the database already contains state, so it makes way more sense to remove RMQ and hold all the state in the database (like they did).
