There are many reasons for deploying containerized application on kubernetes. But we may get overwhelmed with its usefulness and start deploying applications when it should not.
Can there be a case when deploying a application on kubernetes would not add any value and in fact it would be disadvantageous?
To be specific and take an example, would deploying support tool like jenkins on kubernetes be a wrong decision, if scaling and high availability is not really a concern.
Deploying Jenkins or other services on kubernetes can be a good decision if you'd like an existing k8 infrastructure to monitor and manage those pods for you. There is more to k8 than scaling. Running two pods can provide higher availability for example. Maybe you dont need to scale, but you really do not want any downtime. Also, things like rolling updates, etc can be useful in some situations.
I'm finding that deploying anything that requires complex individual configuration and especially data persistence is not awesome in k8 currently. PetSets is aiming to change that but is only Alpha at this point in time.
I suggest avoiding deploying complex database like Cassandra and Vertica in K8. I'd also avoid deploying Elasticsearch, Zookeeper, and Kafka systems in K8. These all require individual node configuration and data persistence that currently will cause you more grief than benefit in my experience.