Cloudflare’s 2021 DyPrIs rollout already felt like the right instinct, isolate the sketchy stuff before you start arguing with microarchitecture, so it’s not shocking that the updated PoC found a hole in the implementation rather than in the basic idea. The original Spectre paper by Kocher et al. in 2018 made it clear this class of bug is really about the surrounding machine, not just the code you think you’re running. The 12 bit/s number is the bit that sticks with me, because on a busy edge box you are fighting interrupts, scheduling noise, and timer fuzz the whole time. V8 Sandbox plus in-process isolation sounds like the kind of belt-and-suspenders move you end up with once you’ve had to prove liveness and confidentiality at the same time.

Glad they published the paper, saving this for later.