Avoid temporal information. Content that describes something only relevant today will be less relevant to readers tomorrow. Avoid adding information that is likely to go stale over time, because we then have to commit to keeping it up to date over time.

For example, we may want to document a new process after a migration, but we don't want to include details of how to migrate, or the historical context about why we migrated. It likely isn't directly relevant to folks trying to understand how to use the current architecture.

Such information however is an excellent candidate for a blog post! Blog posts are well suited for migration details, historical context etc since they are timestamped, and intended to be read in the context of the date it was published.