# Design a polymorphic comments system

Canonical URL: <https://datadriven.io/problems/design-a-polymorphic-comments-system-instead-of-separate-co-ae68456b>

Domain: Data Modeling · Difficulty: medium

## Problem

Design a polymorphic comments system. Instead of separate comment tables per entity, create one comments table that can reference either posts or photos using a commentable_type and commentable_id pattern.

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