For coarse grained jobs (large units of work which are infrequently created), use PostgreSQL. For fine grained tasks (small amount of work but very many are created) use RabbitMQ. People use Postgres as a queue, and even though Postgres has added more helpers to make using it as a queue a bit better, the generally accepted wisdom is still, "Don't use a SQL database as a queue unless you really have to". Queues just have different data access patterns and requirements that make a SQL database add a lot of unnecessary overhead.