The "double data problem" in JavaScript Server-Side Rendering (SSR) frameworks refers to the redundancy of sending the same data twice—once in the HTML output generated by the server and again as serialized data to enable client-side hydration. While addressing this issue may seem beneficial, there are compelling arguments against solving it due to trade-offs in complexity, real-world performance, and developer experience.

1. Complexity and Fragility

Attempting to resolve the double data problem introduces additional complexity in the codebase, as frameworks would need intricate optimizations to avoid sending data twice. This added complexity can make frameworks more fragile and harder to debug, potentially increasing maintenance costs and slowing down development. Solutions to this problem could add more points of failure, making the SSR framework less reliable and harder to work with.

2. Limited Real-World Performance Gains

For many applications, the data being duplicated is often small in size, especially compared to other assets like images, CSS, and JavaScript bundles. In these cases, the actual performance gain from reducing double data transmission is likely marginal, yielding negligible improvements in page load times. When network speed or payload size is not a bottleneck, optimizing SSR hydration to solve the double data problem may not deliver noticeable benefits to the end user.

3. Prioritizing Development Time and Impactful Optimizations

Developers generally need to prioritize optimizations that deliver the most significant impact on user experience. Optimizing for the double data problem may not be the best use of development time, especially when there are other optimizations (like selective hydration or bundling) that could yield greater improvements in user experience. With limited development resources, it may be more effective to focus on optimizations that meaningfully enhance load times and interactivity.

4. Loss of Flexibility and Developer Experience

Existing SSR frameworks that have the double data problem allow for a straightforward approach to data usage, where data can seamlessly be accessed on both the server and client side. Trying to eliminate this redundancy could complicate data handling, requiring developers to track data states more closely and rethink data-fetching patterns. This could make frameworks harder to learn and potentially less intuitive to use, impacting developer productivity and flexibility.

5. Existing Strategies Alleviate Performance Concerns

Many frameworks are already exploring alternative hydration strategies, such as selective hydration, which optimizes performance without addressing the double data problem directly. These strategies allow only essential components to hydrate initially, reducing data transmission costs and improving load times without requiring a full solution to the double data problem. Additionally, techniques like Gzip/Brotli compression and caching minimize the impact of sending data twice by compressing the HTML and JSON payloads, making it more manageable and often negligible.

Conclusion

While the double data problem is an inefficiency, addressing it may not yield substantial real-world benefits for most applications. Solving this issue could lead to increased code complexity, reduced developer flexibility, and only minor performance gains. By focusing on alternative optimizations, such as selective hydration and compression, frameworks can enhance performance effectively without the drawbacks associated with solving the double data problem. Thus, in most cases, it may be more pragmatic to accept this inefficiency rather than introduce new complexities into SSR frameworks.