Kafka at the low end: how bad can it get?

There is oft-quoted advice that Kafka does poorly as a job queue. I’ve experienced this myself, and I wanted to formalize it a bit. I’ll use the common architecture of a Web application submitting background jobs to workers via Kafka (for example, to generate a PDF of some report). Except for the use of Kafka in this role, this is common in Web applications, and (speaking from experience!) when…