Document edge cases

Edge cases represent unusual or extreme scenarios that fall outside typical customer journeys.^[1] While they affect fewer users, these experiences often generate the most frustration and support tickets. Documenting edge cases prevents teams from being blindsided by scenarios they haven't considered.

Common edge cases include system errors, accessibility needs, regulatory exceptions, and unusual user behaviors. For example, customers trying to purchase restricted items, users with expired payment methods, or people accessing services from unsupported regions. These situations require different flows and often manual intervention.

Effective documentation captures not just what happens, but why it matters and how often it occurs. Teams should note the business impact, support costs, and potential solutions for each edge case. This information helps prioritize which edge cases deserve dedicated journey maps versus simple documentation.