Alex Xu

• optimized two C# parsers 800× (30 MB/s → 25 GB/s) and 100× (40 MB/s → 4 GB/s) using SIMD, register allocation tuning, minimizing branches; saved six figures (USD) annually
• troubleshot escalated production issues between Kubernetes, Linux kernel, and networking layers; going from “the jobs aren't starting” through “the queue is too long” down to “the AKS kernel is broken again, built-in curl.exe hangs in Schannel”
• diagnosed Azure TCP checksum corruption causing connection timeouts
• discovered and resolved vulnerabilities from unexpected OAuth app-only/delegated interactions

• built a Buildroot-based minimal Linux and automated OS installer
• developed low-overhead C networking tools and multi-link VPN infrastructure

Reported issues and submitted fixes, including diagnosing cargo build hangs to a kernel pipe buffering bug, and fixed the underlying issue, resolving a deadlock in GNU Make and similar jobservers.

Implemented TLSDESC support, fixing musl compatibility.

Implemented copy_file_range support, shrinking Wine prefixes from 200 MB to less than 1 MB.

Discovered and responsibly disclosed a vulnerability allowing full host device access from guests with virtiofsd enabled.

Reported and fixed various issues, including spurious EPERM, "echo" fails due to free(2) modifying errno, and a Raspberry Pi firmware bug. Proposed optimizations including -fno-plt, compressed debuginfo, and -Os vs -O2.

Implemented cross-bit ptrace, migrated from qmake to CMake, and refactored C++ code.

Built a concurrent Python web font subsetter with automatic pixel-perfect verification, reducing this resume's size from 2 MB to 36 KB.

Built a concurrent Python pygments microservice, reducing TTFB from 1.1s to 0.15s on cgit.alxu.ca. Improved portability and security and reduced LOC by 66% by switching from http.server to aiohttp.

Built a C tunnel to simulate datagrams using TCP packets, fixing TCP-over-TCP overhead.