I'm sure Redis is much faster than an RDBMS w/ all the ACID features turned on. The biggest concern I always have with Redis is simply overwhelming the in-memory storage limits when someone wants to do process a large number of good-sized messages at an inconvenient time. #tradeoffs
Do you also have any idea on the concurrency? How many workers you have pulling from Postgres.
I’ve used this approach before (ages ago) when Redis wasn’t even a thing, though not at high throughout requirements.