Which is Better for JSON API Responses: Flat Arrays or Keyed Objects?

Honestly, if you're already working with large datasets, pagination might be the best route rather than fixating on parsing speed. Sometimes you need the entire set in one go, especially with leaderboards or game state sync. But if your goal is simply parse performance, it might not make a big difference either way.

For most situations, the difference in parsing JSON is negligible. If you're concerned about performance, consider payload size; arrays generally have less overhead because you don't repeat keys. Focus on how you plan to use the data—whether you need fast lookups or if you'll be iterating over the data. If you need both, a common solution is to parse an array and then build a map from it.

Don't get too caught up in optimizing for parse speed. It's often more important to design your data structure around how you'll access it in your application. Think about the user experience and design for that first, and the performance will typically follow naturally.

When you're parsing on the frontend, the speed can depend on a lot of factors like the browser version and machine resources. Benchmarks can vary, so I suggest focusing on how your data will be accessed rather than just parse times. Arrays are often simpler to work with, especially if you're looping through them.

The difference in parsing speed between arrays and keyed objects is usually quite small, especially with modern engines. A good approach might be to focus on sending smaller chunks of data rather than worrying too much about the parse times. Also remember that the server performance also plays a role when retrieving and serving large datasets. For things like leaderboards, you can paginate results to ease the load, which can be more efficient overall.