Abdul Rafay Zahid
Open to work

Systems that hold up when the traffic shows up.

I'm Abdul Rafay Zahid, a backend and systems engineer in Karachi. I scale C++ network gateways, build mail infrastructure that sends 200K+ emails a day, and write the plumbing under AI products.

Resume (PDF)GitHubLinkedInsarbzga@gmail.com
Abdul Rafay Zahid
role
backend and systems engineer
now
Software Engineer, Softaims
base
Karachi, UTC+5
hours
Gulf and EU overlap
open to
remote, EOR, sponsored relocation
learning
Rust, via a terminal music player
200 → 5,000concurrent TLS clients on one C++ gateway
200K+emails a day through infrastructure I built solo
1,000+sending domains with automated DNS lifecycle
~50engineers on the Colloid Swarm harness

Selected work

2005,000

2024/work

200 to 5,000 clients

C++ TLS gateway, 200 to 5,000 concurrent clients

At Ebryx I took a C++ gateway from 200 to 5,000 concurrent TLS WebSocket clients by replacing blocking polling with non-blocking polling, pooling connections, batching Arena requests, and initializing Arena memory up front. Then I stress-tested it past normal traffic and fixed the failure paths that only showed up there, including a log-rotation race that removed a file between check and read and crashed a worker thread. The same platform got an auto-update migration system for its move to multi-tenancy and a component ported from x86-64 to ARM for on-prem deployment.

stack: C++, TLS, WebSocket, Linux, Python, MySQL

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2026/work

200K+ / day

Mailstation, enterprise email infrastructure

A production email platform built alone in about two months. A multi-channel campaign engine with A/B logic and threaded follow-ups sits on KumoMTA and Amazon SES edge nodes, each running a Python agent daemon. Automated SPF, DKIM, and DMARC lifecycle, Redis-locked graduated warmup, blacklist monitoring, and bi-directional Salesforce sync. It replaced the Salesforce email tool it was measured against and beat it on campaign response rates.

stack: Python, FastAPI, PostgreSQL, Redis, Celery, KumoMTA, AWS SES, React

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review gate

2026/open source

7 personas, 3 tiers

Colloid Swarm

A portable multi-agent development scaffold, adopted as the company-wide engineering harness for roughly 50 engineers. Seven delegating personas route work across three cost and capability tiers, planning and architecture stay at the top tier, and hostile review runs as an independent gate rather than the implementer grading its own work. Canonical instructions, skills, hook policies, and the MCP server registry live in one engine-neutral layer with thin adapters for Claude Code, Codex, Kimi, and GitHub Copilot. An exporter transplants the scaffold into a target repository at a pinned commit.

stack: Python, Bash, Claude Code, Codex, MCP

View on GitHub

Smaller pieces

  1. 2025NPI Discovery ServiceBulk export from a registry that caps every query, without silent truncation.
    partition-aware

    Search and bulk-export US healthcare providers from the public NPPES registry. A partition-aware collector splits by provider type and then narrows by postal prefix until each leaf query fits within upstream result limits, and reports incomplete partitions in response metadata rather than silently truncating. Redis-backed caching, a WebSocket gateway streaming bulk-job progress across API instances, correlation-ID middleware for end-to-end tracing, Terraform-provisioned deploys.

    stack: TypeScript, NestJS, Next.js, Redis, Terraform

    View on GitHub
  2. 2025WARPOWhatsApp backup decryption and export for Android and iOS.
    38dc6da60c2c8bbe2544936759ceef1743262aa06c47e24a39bb0c6d52f6182e737782c664495de62bc4377cfa00907eee2795dd64fbb890995c2c607b9e525101feef1eaef0a5561982669ba4cd4e2152fc7d8d23b9fb66acdcfa09e6db7d498593c7b66aa348e06e135c5d84bcaa53a69bc6bcbbc72221746361846224bbdbbcffd13c2f0b33aa8d4e897238d4677c362fca7a6541ebc9338974532f258102a2dde553f915b31f6c408f1c5462bd57c203f32bdde2073b45ef771a84aea949993c13f0f40fcrypt12 / 14 / 15

    A WhatsApp chat exporter for Android (crypt12, crypt14, crypt15) and iOS backups. Decrypts the database formats, handles key extraction, and writes the conversations out as HTML and JSON. The kind of binary-format work that is hard to fake, which is the point.

    stack: Python, SQLite

    View on GitHub
  3. 2022Balloon game in 8086 assemblyDirect video memory, a hooked hardware timer, no BIOS calls.
    0xB800

    A DOS text-mode animation in 8086 assembly. Writes directly to the CGA video buffer at segment 0xB800 with no BIOS or DOS print calls, hooks the IRQ 0 hardware timer through the interrupt vector table to drive a live tick counter, and implements custom scroll, clear, and draw routines on a stack-based calling convention.

    stack: 8086 assembly, DOS

    View on GitHub
  4. 2024Real-time facial emotion recognitionA CNN trained from scratch on FER2013, running live on camera frames.
    28,709 images, 7 classes

    A convolutional neural network trained from scratch on the FER2013 training set (28,709 images across 7 emotion classes) with a real-time inference loop in OpenCV: Haar-cascade face detection, 48x48 grayscale crop, per-frame prediction, and an on-frame label. Exported to ONNX for on-device inference inside a Unity game, the basis of my final-year project on gamified emotional-development intervention.

    stack: Python, PyTorch, OpenCV, ONNX, Unity

    View on GitHub
  5. 2025Music ToolsA Discord bot streaming a GitHub-backed music library with no local storage.
    48 kHz PCM

    A Node.js monorepo for a GitHub-backed personal music library: a Discord bot that streams audio on demand from a private repository with no local storage, transcoding to 16-bit PCM at 48 kHz through ffmpeg and preloading the next queued track to avoid dropouts, plus CLI tools for downloading, uploading, and listing tracks.

    stack: Node.js, ffmpeg, Discord API

    View on GitHub
  6. 2021Candy Crush cloneA match-three game from scratch in C++ and SFML.
    C++ / SFML

    A match-three game built from scratch in C++ and SFML. An early deep dive into graphics programming: shaders, sprite rendering, and the difference between dynamic and static linking. Special candy combinations, save and load, and scoring.

    stack: C++, SFML

    View on GitHub

Writing

Now

Building

A voice onboarding agent whose backend keeps the whole interview replayable offline, with exactly-once writes and per-session locking.

Learning

Rust, by building a terminal music player. I already think in ownership and lifetimes from C++; Rust makes the compiler check it.

Drawn to

Computer vision, robotics, and autonomy, specifically the backend and infrastructure side of hard-tech.

Building something that has to hold up under load? Let's talk.

sarbzga@gmail.com·replies within a day, Karachi time