Performance analysis requires deep React internals knowledge and benchmarking expertise
The issue involves analyzing and improving RSC rendering pipeline performance through benchmarking and potential optimizations. It requires understanding React's internals, performance profiling, and working with custom forks. The scope is somewhat clear but involves complex performance considerations.
React version: 19.3.0-canary-c0d218f0-20260324 and uhh, a custom fork
I am working on a new RSC-based framework. There's been a lot of recent discussion around react-based frameworks' performance in what are generally not representative of real world performance (aren't all web benchmarks?), but they did uncover some serious gaps. RSC performance is honestly sufficient for most use-cases, but it could be much more efficient and gets very throttled very quickly.
I spent a lot of time digging into RSC rendering throughput today+yesterday with claude. Both in next and outside of next (w/ my new framework, some pure react, etc.). I found two small perf wins in both Fizz and Flight (sent a PR for Fizz), but they are minimal in comparison to the two below. I spent most of the day debugging real world scenarios: code running on the same k8s cluster across the same apps in different contexts (next, my framework, etc.) all running through real-world networks. I then dropped down to baseline benchmarks to try and isolate the problems which reflected my real-world testing.
This is all based on single core, single threaded rendering. If I got anything wrong here, if I shoved my foot in my mouth, if I over-dramatized the situation, please tell me. I'm not an expert in web throughput engineering, cpu architectures, or javascript/react internals. I'm just a long-time software engineer who's having way too much fun building my own framework on what I consider to be the most complete web architecture.
These benchmarks are run in
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