Having the ability to set a TTL on the cache key is a critical feature of a cache, not something that can be tacked on later. I always find these "don't use redis" posts kind of strange. Redis is so simple to operate at any scale, I don't quite get why it is important to remove it.
Don't get me wrong, the idea that he wants to just use a RDMBS because his needs aren't great enough, is a perfectly inoffensive conclusion. The path that led him there is very unpersuasive.
It's also dangerous. Ultimately the author is willing to do a bit more work rather than learn something new. This works because he's using a popular tool people like. But overall, he doesn't demonstrate he's even thought about any of the things I'd consider most important; he just sort of assumes running a Redis is going to be hard and he'd rather not mess with it.
To me, the real question is just cost vs. how much load the DB can even take. My most important Redis cluster basically exists to take load off the DB, which takes high load even by simple queries. Using the DB as a cache only works if your issue is expensive queries.
I think there's an appeal that this guy reaches the conclusion someone wants to hear, and it's not an unreasonable conclusion, but it creates the illusion the reasoning he used to get there was solid.
I mean, if you take the same logic, cross out the word Postgres, and write in "Elasticsearch," and now it's an article about a guy who wants to cache in Elasticsearch because it's good enough, and he uses the exact same arguments about how he'll just write some jobs to handle expiry--is this still sounding like solid, reasonable logic? No it's crazy.