Exploring Threaded Commenting Systems: From Recursion to Flat Mapping

Developing an intuitive and flexible threaded commenting system is a common challenge in web development. Whether building a discussion platform, a forum, or a social media feature, the approach to designing nested comments can significantly affect performance and user experience. In this article, we’ll journey through different strategies—starting with recursion, moving to a flat map structure, and finally contemplating issues around loading more comments dynamically.

The Initial Approach: Recursive Components

Traditionally, implementing nested comments involves recursive component structures. Each comment component renders its child comments by embedding itself recursively. This method is straightforward and mirrors the hierarchical nature of discussions.

However, as the depth of nesting increases, this approach can introduce complexity. Managing logic within each comment component tends to clutter the codebase, making maintenance and enhancements more cumbersome. In a recent project, I found that embedding too much logic into the comment components hindered scalability.

Refactoring Toward Dumb Components and Centralized Logic

To improve clarity and manageability, I transitioned to making individual comment components “dumb”—focusing solely on presentation—and consolidating the core logic into a main CommentSection. This parent component oversees data fetching, state management, and rendering logic, simplifying individual comment components and enabling easier updates.

Adopting a Tree Structure with Node Types

Initially, I maintained a flexible tree of comment nodes representing the hierarchical relationships. This allowed intuitive navigation and rendering of nested comments. However, managing such trees comes with its own stroke of complexity, especially when dealing with dynamic loading and large datasets.

Following advice from development best practices, I shifted toward a “split-graph” structure. Decoupling the data relationships from direct tree management reduces type management headaches and allows for more flexible data handling, especially when implementing features like lazy loading or pagination.

Data Fetching Strategies: Recursive vs. Flat

Early in development, I explored recursive database operations—fetching comments and their children recursively, then sorting and rendering them client-side. While this seemed logical, performance issues surfaced due to deep recursion and the volume of data transferred.

To mitigate this, I revised the approach: performing sorting and filtering within database queries via RPC calls. By returning a flat list of comments annotated with depth or indentation levels, the client-side operates on a simplified data structure, improving performance and scalability.

Handling “Load More” Functionality

One of the persistent challenges is detecting when to display a “load more” button for comments with