Sincerely (Feel the need to add that given the tension around here in these comments), I'm curious how Redis was annoying. Can you give any detail/insight?

Every component takes work. You have to upgrade it, something goes wrong with tuning, you have to debug it, etc. It went wrong about once a month, somehow. I'm sure it was fixable, but time is a commodity, and not having it any more gives us more time to work on other things.

We can't get rid of Postgres, but since we run Postgres on GCP we really never even think about it.