Kafka requirements for mod-pubsub and Data-Import modules

What is the expectation of Kakfa data persistence for mod-pubsub? Looking for requirements or parameters to keep in mind when tuning Kafka for production deployment. In particular, configuring data log retention size and data log retention time. Does pubsub expect messages to be persisted indefinitely, for a relatively long time, or just until the consumers have had a chance to see the message?

Tuning Kafka will of course depend on the traffic a system gets, but looking for some rough guidelines.
Some of this depends on outcomes of current work with the PTF

Be sure to document in the Iris Release Notes

extend https://wiki.folio.org/login.action?os_destination=%2Fpages%2Fviewpage.action%3FspaceKey%3DFOLIJET%26title%3DChecklist%2Bfor%2BData-Import%2Bapplication%2Bsetup%2Bon%2Ba%2Bnew%2Benvironment&permissionViolation=true

Background:

• Create a new page on the wiki: https://wiki.folio.org/display/FOLIJET/Checklist+for+Data-Import+application+setup+on+a+new+environment
• Add note and link to the new page in the Iris release notes: https://wiki.folio.org/display/REL/R1+2021+%28Iris%29+Release+Notes
• Describe steps to check env variables, module params
• Troubleshooting steps