Without the context, it is hard to know what this means. If they are a company that heavily uses Kafka, then there could well be an expectation that you would h

Without the context, it is hard to know what this means. If they are a company that heavily uses Kafka, then there could well be an expectation that you would have researched it and at least learned enough to have an informed discussion. Other employers might expect someone who is "Senior" to know about what different languages offer. As others have said, the title "Senior" means different things to different people and not all skills are transferable. As others have said, if they don't do interviews well, don't sweat it, you probably don't want to work there anyway!