TLDR: I do not recommend using bcache with btrfs, but this is a sample of 1.

I've been using bcache (SSD) with btrfs (4TB hard drive) for while, and am in the process of ripping it out. What I found is the filesystem gets wedged if there is a heavy write load (lots of files) such as running debootstrap. This happened with both write-through and write-back. The symptoms are all requests stall and a kernel log message about hung btrfs tasks. Only a reboot (typically needing sysrq keys to complete) works.

The problem did not occur previously when using btrfs without bcache and the same workload. It also doesn't occur during "lighter" workloads.

See under the status headline on http://bcachefs.org/ and decide for yourself whether that's good enough for your use case.

Wrong filesystem. bcache is the one that sits in front of another filesystem, and improves its performance. bcachefs (your link) is from the same author, but is a standalone filesystem.

https://en.wikipedia.org/wiki/Bcache

I've asked about both, but it's always good to clear things out.

I have been using a BCache (SSD) in front of a BtrFS Native RAID (HDD) for quite a while without issue.