4:19

> 2025-09-26
Cloudflare just got faster and more secure, powered by Rust
https://blog.cloudflare.com/20-percent-internet-upgrade/

4:20

> 2025-11-18
Cloudflare outage on November 18, 2025
https://blog.cloudflare.com/18-november-2025-outage/

Each module running on our proxy service has a number of limits in place to avoid unbounded memory consumption and to preallocate memory as a performance optimization. In this specific instance, the Bot Management system has a limit on the number of machine learning features that can be used at runtime. Currently that limit is set to 200, well above our current use of ~60 features. Again, the limit exists because for performance reasons we preallocate memory for the features.

When the bad file with more than 200 features was propagated to our servers, this limit was hit — resulting in the system panicking. The FL2 Rust code that makes the check and was the source of the unhandled error is shown below:

This resulted in the following panic which in turn resulted in a 5xx error:

thread fl2_worker_thread panicked: called Result::unwrap() on an Err value