Klaus Werner Senior Rust Developer
Berlin, Germany (Remote) • rustdev@gmail.com • +49 30 555 0182
Profile Summary
- Senior Rust Developer with 8 years of experience building memory-safe systems Rust at infrastructure scale across virtualization platforms, container runtimes, and Linux distribution tooling, specializing in ownership and lifetime design, Tokio async runtimes, and unsafe FFI with safety invariants.
- Hands-on coverage across Rust (Rust 2021 edition), async runtime (Tokio), web stack (Axum), persistence (SQLx, PostgreSQL), and Wasm and embedded (wasm-bindgen, clap) with strong fundamentals in ownership and borrowing, traits and generics, Result and Option handling, and a working command of pinning, async traits, and lifetimes.
- Deep expertise in ownership and lifetime modeling, async Tokio task scheduling, unsafe FFI with safety invariants, and zero-cost abstractions and SIMD tuning, applying methodologies such as working with the borrow checker over fighting it and proptest, miri, and cargo-fuzz coverage on unsafe code to deliver memory-safe, low-latency Rust services that hold the line under production load.
- Engaged collaborator working cross-functionally with Kernel, Security, Platform, and SRE teams in open-source-first and async-friendly remote teams, contributing to RFC threads, on-call rotations, and architecture reviews with an ownership-first mindset and clean handoffs.
- Mentor who shares technical excellence and fosters a culture of memory safety and performance discipline through PR reviews and pattern docs, while running Rust guild and unsafe-review sessions and authoring widely used crate and unsafe-block templates.
Technical Skills
- Languages & Core Rust:
- Rust 2021 edition, Rust 2024 edition, traits, generics, lifetimes, pattern matching, enums, Result, Option, error handling with thiserror and anyhow, macros
- Async & Concurrency:
- Tokio, async-std, smol, futures, pinning, async traits, channels, Arc, Mutex, RwLock, atomics, Rayon, crossbeam
- Web & Backend:
- Axum, Actix Web, Rocket, Warp, Tower, hyper, reqwest, tonic, SQLx, sea-orm, Diesel, PostgreSQL, Redis, OpenAPI
- Systems & Performance:
- unsafe Rust, raw pointers, MaybeUninit, perf, flamegraph, cargo-flamegraph, criterion, hyperfine, SIMD, std::arch, zero-cost abstractions, cache-friendly layouts
- Wasm, CLI & Embedded:
- wasm-bindgen, web-sys, Wasmtime, Wasmer, Extism, Cloudflare Workers, Spin, clap, ratatui, no_std, embassy, RTIC, cortex-m
- Testing, Tooling & Quality:
- cargo test, criterion, proptest, quickcheck, cargo-fuzz, libFuzzer, AFL, clippy, rustfmt, miri, cargo audit, cargo deny, cargo workspaces
- Interop, FFI & Polyglot:
- bindgen, cbindgen, PyO3, maturin, NAPI-RS, neon, cxx, JNI, FFI safety patterns, Send and Sync, Pin and Unpin, repr(C)
- Build, Toolchain & CI/CD:
- Cargo, rustup, cross-compilation, musl static binaries, Docker distroless, GitHub Actions, GitLab CI, semver release flow, tracing, OpenTelemetry
Education
Technische Universität
Berlin
M.S. in Computer
Science
Work Experience
AWS
(Bottlerocket)
Senior Rust
Developer
- Owned idiomatic Rust development end to end on the container-optimized Linux distribution for EKS and ECS running across 2.4M hosts, shipping update agent, API server, and bootstrap controller across 24 crates held to the Rust API guidelines and the project's own RFC review bar.
- Mastered ownership, borrowing, and lifetimes with borrowed views over owned config trees with explicit 'a lifetimes, Cow for borrowed-or-owned data flow, and Box and Rc only where the model demands it, removing 312 unnecessary clones and dropping workspace compile time from 9.4min to 2.8min.
- Owned memory safety and unsafe Rust through audited unsafe blocks around raw syscalls and FFI with documented safety invariants, a minimal blast-radius policy that keeps every unsafe scope under ten lines, and module-level SAFETY comments on each one, auditing 84 unsafe blocks and holding miri coverage on the unsafe surface at 100%.
- Drove async programming and concurrency on Tokio multi-threaded runtime with bounded mpsc channels and Arc<RwLock> shared state, tokio::select for cancellation, and Rayon for the data-parallel diff stage, capping concurrent tasks at 4096 and dropping lock contention on the hot path from 38% to 4%.
- Tuned systems and performance with cargo-flamegraph profiling with criterion regression gates and cache-friendly layouts, perf event sampling, and SIMD via std::arch on the verification path, dropping p99 update apply latency from 820ms to 95ms and cutting heap allocations on the hot path by 74%.
- Built the web and back-end control plane on Axum with Tower middleware, SQLx connection pooling, and tonic for gRPC control plane, hyper for low-level transport, and reqwest for outbound calls, shipping 110+ endpoints behind a typed handler layer and holding service uptime at 99.99% across the last four quarters.
- Shipped WebAssembly modules with Wasmtime-hosted policy plugins with Extism plugin SDK and capability-based sandboxing, wasm-bindgen for the operator console UI, and a thin host ABI documented per release, landing 32 modules in production and cutting plugin cold-start from 180ms to 14ms.
Mozilla
Software Engineer
(Rust)
- Drove testing, tooling, and code quality with proptest property tests, cargo-fuzz harnesses, and criterion regression gates, clippy and rustfmt on every PR, and miri runs on the unsafe surface, dropping crash-bug rate per release from 42 down to 6 and lifting cargo-fuzz coverage on the parser surface to 91%.
- Built CLI and embedded-leaning tooling with clap-driven CLIs cross-compiled to 6 targets with musl static binaries, a ratatui-based debugger TUI, and no_std prototypes on cortex-m boards, shipping across 6 targets and shrinking the release binary from 42MB to 4.2MB.
- Owned interop and FFI work through PyO3 bindings exposed via maturin and cbindgen-generated C headers for the C++ host, NAPI-RS shims for the Node tooling, and a documented Send and Sync policy on every shared type, bridging 4 host languages without a single use-after-free regression over the run.
- Strengthened idiomatic Rust foundations across the team through trait-based design, Result and Option flows, and newtype patterns over raw primitives, module layout reviews, and Rust Book reading sessions, while mentoring 5 engineers through pair-programming, code-review checklists, and a written Rust idiom guide adopted across two squads.