--- title: Rust rewrites go mainstream, formal verification lands... description: This week the big theme is Rust rewrites getting cheaper and higher-stakes at the same time. AWS shipped a formally verified hypervisor written in a Rust... canonical: https://daily.dev/posts/rust-rewrites-go-mainstream-formal-verification-lands-in-ec2-x8uztmtct twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Rust rewrites go mainstream, formal verification lands in EC2 | daily.dev og:description: This week the big theme is Rust rewrites getting cheaper and higher-stakes at the same time. AWS shipped a formally verified hypervisor written in a Rust... og:url: https://daily.dev/posts/rust-rewrites-go-mainstream-formal-verification-lands-in-ec2-x8uztmtct og:image: https://api.daily.dev/og/posts/x8uzTmTcT.png og:image:alt: Rust rewrites go mainstream, formal verification lands in EC2 og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Rust rewrites go mainstream, formal verification lands in EC2 **[Rust Digest](https://daily.dev/sources/rust_digest)** · 4 min read · 6 upvotes · 0 comments ## Summary This week the big theme is Rust rewrites getting cheaper and higher-stakes at the same time. AWS shipped a formally verified hypervisor written in a Rust subset for its newest EC2 instances, while Discord detailed the messy reality of moving 80% of its voice traffic onto Cloudflare's edge. Multiple posts made the case that AI-assisted rewrites have made large Rust migrations economically viable, with concrete numbers from Bun, Meta, and ExpressVPN. Meanwhile the Rust project itself is tightening the bolts, adding semver-checking CI to the standard library and a formal policy restricting AI-authored commits to its own repo. ## Content **TLDR:** This week the big theme is Rust rewrites getting cheaper and higher-stakes at the same time. AWS shipped a formally verified hypervisor written in a Rust subset for its newest EC2 instances, while Discord detailed the messy reality of moving 80% of its voice traffic onto Cloudflare's edge. Multiple posts made the case that AI-assisted rewrites have made large Rust migrations economically viable, with concrete numbers from Bun, Meta, and ExpressVPN. Meanwhile the Rust project itself is tightening the bolts, adding semver-checking CI to the standard library and a formal policy restricting AI-authored commits to its own repo. --- ## AWS ships formally verified hypervisor written in a restricted Rust subset The new Nitro Isolation Engine behind Graviton5-powered M9g/M9gd instances is a separation kernel written in μRust, with 330,000 lines of machine-checked Isabelle/HOL proofs covering confidentiality, integrity, and memory safety. AWS is calling it the first formally verified hypervisor running in a commercial cloud, putting it in the same league as seL4. Worth watching if you care about what 'proven correct' actually looks like at hyperscaler scale, not just in academic toy examples. [Read more](https://daily.dev/posts/xonDXKppx) ## Discord's Cloudflare voice migration hit NIC contention, 25-second VM freezes, and a Rust SFU bug Moving 80% of Discord's voice and video traffic to Cloudflare's edge surfaced a pile of gnarly infrastructure bugs: an ISP peering bottleneck in Rotterdam, page-cache flush stalls that froze VMs for up to 25 seconds, and a write-starvation bug in their Rust SFU combined with softirq scheduling contention that caused European ping spikes into 2026. The fixes are the interesting part - a nine-millisecond flush budget in the Tokio event loop and CPU affinity pinning via taskset got Frankfurt to 34% lower ping and 42% less packet loss versus the old vendor. This is a good read if you're running anything latency-sensitive on shared cloud infrastructure. [Read more](https://daily.dev/posts/XeEigwjRP) ## AI-assisted Rust rewrites rack up real numbers: Bun, Meta, Cloudflare, ExpressVPN The economics of full rewrites have shifted enough that people are actually doing them now. Bun reportedly ported 535,000 lines of Zig to Rust in 11 days for $165,000 using Claude agents, versus an estimated year of engineer time. Meta's OCaml-to-Rust port of its Flow type checker got roughly 2x performance, Cloudflare's Rust proxy FL2 shaved 10ms off median response times versus its old Nginx setup, and ExpressVPN's Rust rewrite of its Lightway protocol hit up to 2x speed on routers and nearly 4x throughput on iOS. Separately, Greg Kroah-Hartman is now on record calling Rust the future of Linux, citing 113,000 lines of Rust already in the kernel and the claim that 80% of past kernel CVEs would have been prevented by it. [Read more](https://daily.dev/feed-by-ids?id=m7YK7LZjF&id=HOjJkxkqz&id=cSCZMZvt1&id=PzP9w9MwS) ## Rust project locks down AI-authored commits and adds semver CI to the standard library Two governance moves worth knowing about if you contribute upstream. The Rust core repo now has a formal LLM usage policy requiring an 'ai-assisted' disclosure label for AI-written code, plus a circuit breaker that pauses AI-authored merges if they exceed half of all merges in a six-week window. Separately, the standard library now runs cargo-semver-checks in CI, closing gaps that let unstable-method or soundness fixes accidentally break stable code in the past (the async-std 2020 incident, the tokio 1.94 breakage that forced a 1.94.1 point release). Took 15,000+ lines of code and months of work to teach the tool about Rust's stability attributes. [Read more](https://daily.dev/feed-by-ids?id=nPr4Hm4Wd&id=6185skjIf) --- ## Also notable - **fearless_simd v0.7 adds 64-bit integer support ahead of v1.0:** fearless_simd v0.7 completes u64/i64 vector coverage, adds an SSE2 fallback level, and unifies generic bitcasting via a new Bytes trait, with build times unchanged from v0.6 and v1.0 planned for early September. [Read more](https://daily.dev/posts/Aors3lFEX) - **VectorWare runs Rust's portable SIMD directly on the GPU:** By mapping core::simd's Simd onto CUDA warp lanes, the same nightly-only SIMD source code now runs unchanged on both CPU and GPU, though the zero-cost property only holds when vector width exactly matches warp width. [Read more](https://daily.dev/posts/ViJtJxHGd) - **Redox OS cuts context-switch benchmark from 1.15µs to 250ns:** Redox Summer of Code scheduler and context-switching work dropped a synthetic benchmark from roughly 1.15 microseconds to 250 nanoseconds, alongside a new GUI installer and ported uutils grep/sed. [Read more](https://daily.dev/posts/iD2vJuIxZ) - **Tail-call dispatch benchmarks: direct dispatch beats subroutine threading 3x in Rust VMs:** Using the unstable explicit_tail_calls feature (become keyword), direct dispatch hit 24.59ns versus 79.93ns for subroutine threading on a stack machine benchmark, giving interpreter authors a concrete number to weigh against `dyn Fn` call overhead. [Read more](https://daily.dev/posts/BOtv3oteV) - **RFC 3323 lands on nightly: compiler-enforced trait and field mutation restrictions:** The impl_restriction and mut_restriction features are now testable on nightly, replacing the verbose sealed-trait pattern with syntax like `pub impl(crate) trait Foo` and `pub mut(crate) alpha: u8`. [Read more](https://daily.dev/posts/ZncAKna0d) ## Similar posts on daily.dev - [Rewriting in Rust: Performance, Failures, 2026 Reality Check](https://daily.dev/posts/rewriting-in-rust-performance-failures-2026-reality-check-pzp9w9mws) · JetBrains · 5 upvotes · 0 comments --- Tags: [#aws](https://daily.dev/tags/aws), [#rust](https://daily.dev/tags/rust), [#ai-coding](https://daily.dev/tags/ai-coding) [View this post on daily.dev](https://daily.dev/posts/rust-rewrites-go-mainstream-formal-verification-lands-in-ec2-x8uztmtct) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"DiscussionForumPosting","mainEntityOfPage":"https://daily.dev/posts/rust-rewrites-go-mainstream-formal-verification-lands-in-ec2-x8uztmtct","headline":"Rust rewrites go mainstream, formal verification lands in EC2","text":"This week the big theme is Rust rewrites getting cheaper and higher-stakes at the same time. 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