Seroval draws performance down on large payloads

[kompot]

Which project does this relate to?

Router

Describe the bug

We've found that using default seroval serialization for our @tanstack/react-router-ssr-query backed SSR app leads to pretty significant performance penalties on large payloads.

We have big (8mb uncompressed JSON) catalog of items that is:

• cached in SSR workers, used to reduce it to a pretty small HTML output on initial request
• streams catalog of items in JSON when HTML/CSS is already being processed

This way we get best of both worlds: no extra request client side and pretty fast LCP as JSON to hydrate is streamed.

But we've found that using default transport gives us around 50% performance penalty. In a real world production app with this 8mb streamed catalog we get ~24rps and ~180ms avg latency (4 node workers, autocannon it locally, all API data is cached). With a hacked transport (where we've replaced seroval with JSON.stringify) — ~36rps and ~120ms avg latency.

To confirm the point I've created a repo (https://github.com/kompot/seroval-vs-jsonstringify) that has a benchmark of seroval vs JSON.stringify and gives kind of the same numbers. 10mb serialization on a fast machine takes 70ms in seroval and 7ms with JSON.stringify

Complete minimal reproducer

https://github.com/kompot/seroval-vs-jsonstringify

Steps to Reproduce the Bug

Run a test, confirm a point that seroval leads to performance penalties even on small payloads.

Expected behavior

I would suggest an option to opt out of seroval in @tanstack/react-router-ssr-query at least for payload body. I guess that 99+% of payloads in real worlds apps are plain JSON does not need to fight problems seroval was created for — serialize any JS object.

Screenshots or Videos

No response

Platform

• Router / Start Version: @tanstack/react-start@1.168.25, @tanstack/react-router@1.170.15, @tanstack/router-core@1.171.13
• OS: macOS/Linux
• Browser: n/a
• Browser Version: n/a
• Bundler: vite
• Bundler Version: 8.0.x

Additional context

No response

[lxsmnsyc]

Hi, author of seroval here.

I'm pretty much aware of this performance cost from the beginning (see https://github.com/lxsmnsyc/seroval/blob/main/benchmark/results/csv/large-complex-collection%20to%20string.csv), and I believe the TanStack team are pretty much aware of this too.

Comparing to JSON.stringify in terms of perf is always unjustifiable since most JSON.stringify and JSON.parse implementations run on lower-level (as in, closer to metal). We can't get near to that kind of performance, let alone half of it. It's the cost to pay for object deduping, extended serialization capability and streaming data.

[kompot]

Sure, I understand there are benefits of using seroval for generic use. Just wanted to validate idea of opting out for @tanstack/react-router-ssr-query payload cases. From my point of view it looks valid but would be glad to hear other opinions.