Hello, I'm

Congfei Zhang

ML engineer building ads ranking systems at scale. Astrophotographer chasing the Milky Way. Cat dad. Perpetual explorer of mountains, oceans, and code.

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Professional Journey

Building Systems at Scale

From recommendation engines to ads ranking, I build ML systems at scale.

May 2024 — Present

Snap Inc.

Senior Machine Learning Engineer · Tech Lead
Bellevue, WA

Tech lead for DPA (Dynamic Product Ads) ranking. Focused on end-to-end ads ranking — retrieval, conversion optimization, feature strategy, and privacy-preserving modeling. Currently building an LLM-agent-based retrieval system.

Ads Ranking Retrieval LLM Agents Privacy
Feb 2022 — Feb 2024

Stealth Startup

Co-Founder & Technical Lead

Co-founded and led the technical vision for a next-gen social media platform built in Rust. Drove architecture decisions across the stack — from multi-modal recommendation systems to backend infrastructure.

Rust Founder RecSys Architecture
Jun 2021 — Feb 2022

Amazon Ads

Applied Scientist II
Seattle, WA

Led end-to-end development of a large-scale campaign recommendation system on AWS, from requirements to data pipelines to serving.

AWS Airflow Recommendations
Mar 2019 — Jun 2021

Kwai AI Lab

Research Engineer & Scientist
Bellevue, WA

Built intelligent targeting systems and optimized CTR/CVR models for ads. Co-created Persia — an open-source distributed training framework for large-scale recommenders. Published at KDD 2022.

Persia KDD 2022 CTR/CVR Distributed ML

University of Wisconsin-Madison

M.S. Industrial Engineering
2018

Shanghai Jiao Tong University

B.S. Mechanical Engineering (UMich-SJTU Joint Institute)
2017

Through My Lens

Capturing Moments

Landscapes, astrophotography, figure photography, and everything in between.

Figure on green hillsideFigure on green hillside
Green Horizons
Figure in red azaleasFigure in red azaleas
Crimson Bloom
Figure with fire effectsFigure with fire effects
Flame & Ribbon
Alpine volcanic slopeAlpine volcanic slope
Volcanic Slopes
Deer pair on mountain ridgeDeer pair on mountain ridge
Mountain Pair
Figure in wildflower meadowFigure in wildflower meadow
Wildflower Meadow
Figure with fire effects alternateFigure with fire effects alternate
Crimson Glow
Figure with glowing lanternFigure with glowing lantern
Lantern Light
Figure by mountain lakeFigure by mountain lake
Mirror Lake
Figure in dandelion fieldFigure in dandelion field
Dandelion Dreams
Foxglove by mountain lakeFoxglove by mountain lake
Alpine Foxglove
Figure with lupine and peaksFigure with lupine and peaks
Lupine & Peaks
Figure among snowdropsFigure among snowdrops
Spring Whisper
Figure in ocean surf at sunsetFigure in ocean surf at sunset
Golden Surf
Figure among purple flowersFigure among purple flowers
Purple Garden
Figure on seaside rockFigure on seaside rock
Seaside Rest
Milky Way with green airglowMilky Way with green airglow
Airglow Night
Figure in spring parkFigure in spring park
Spring Meadow
Figure on rock close-upFigure on rock close-up
Coastal Close-up
Milky Way panorama with meteorMilky Way panorama with meteor
Meteor Streak
Figure in mixed flower fieldFigure in mixed flower field
Mixed Blooms
Tranquil mountain lakeTranquil mountain lake
Tranquil Lake
Figure at modern glass buildingFigure at modern glass building
Glass & Light
Figure among rhododendronsFigure among rhododendrons
Rhododendron Garden
Figure by lakeshoreFigure by lakeshore
Golden Lakeshore
Figure in nemophila fieldFigure in nemophila field
Blue Nemophila Sea
Milky Way over Mount RainierMilky Way over Mount Rainier
Milky Way over Mount Rainier
Miku on beach rocksFigure on beach rocks
Turquoise Shore
Figure among blue flowersFigure among blue flowers
Blue Portrait
Figure in deep snowFigure in deep snow
Snow Serenade
Figure among daisiesFigure among daisies
Daisy Field
Figure with warm spotlightFigure with warm spotlight
Warm Spotlight
Figure over turquoise lakeFigure over turquoise lake
Diablo Lake
Figure in nemophila golden lightFigure in nemophila golden light
Golden Wanderer
Winged figure with bokeh waterWinged figure with bokeh water
Ocean Bokeh
Deer in misty forestDeer in misty forest
Morning Herd
Figure among balsamrootFigure among balsamroot
Balsamroot Hills
Winged figure on rocky shoreWinged figure on rocky shore
Sunset Guardian
Figure on snowy mountainFigure on snowy mountain
Glacier Summit
Figure buried in snowFigure buried in snow
Snow Angel
Deer on alpine meadowDeer on alpine meadow
Alpine Grazer
Winged figure facing sunsetWinged figure facing sunset
Horizon Watch
Figure with Space NeedleFigure with Space Needle
Kerry Park
Vertical Milky Way over RainierVertical Milky Way over Rainier
Starlit Summit
Figure in nemophila sunlitFigure in nemophila sunlit
Sunlit Blooms
Figure on mountain valleyFigure on mountain valley
Valley Overlook
Campervan under the Milky WayCampervan under the Milky Way
Under the Stars
Figure in alpine wildflowersFigure in alpine wildflowers
Alpine Wildflowers
Figure on pebble beachFigure on pebble beach
Golden Hour
Winged figure on beach at duskWinged figure on beach at dusk
Sunset Wings
Milky Way over Mount BakerMilky Way over Mount Baker
Mount Baker Nights
Winged figure with Seattle skylineWinged figure with Seattle skyline
Seattle Wings
Mountain panorama with light raysMountain panorama with light rays
Mountain Vista
Winding mountain road in fogWinding mountain road in fog
Into the Mist
Deer on misty hilltopDeer on misty hilltop
Ridgeline Deer
Seattle skyline panoramaSeattle skyline panorama
Seattle Skyline
Winged figure silhouetteWinged figure silhouette
Silhouette
Milky Way core above RainierMilky Way core above Rainier
Milky Way Core
Starry sky with lake reflectionStarry sky with lake reflection
Starlit Reflection
Figure with Cascades peakFigure with Cascades peak
Cascades View

Adventures

Places I've Explored

From the Pacific Northwest to distant shores — chasing light, altitude, and good food.

Pacific NorthwestPacific Northwest
Pacific Northwest
Milky Way hunts and mountain hikes around Mt. Rainier
Olympic MountainsOlympic Mountains
Olympic Mountains
Misty ridges and endless green valleys
Road TripsRoad Trips
Campervan Adventures
Life on the road under a canopy of stars
Coastal TravelsCoastal Travels
Coastal Explorations
Dramatic sunsets and open horizons

The Real Bosses

Meet My Cats

The ones who actually run the household. Professional nappers, window watchers, and chaos engineers.

Cat yawningCat yawning

Big Yawn Energy

Caught mid-roar (or mid-nap, hard to tell)

Cat gazingCat gazing

Window Gazer

Contemplating the meaning of birds

Orange cat relaxingOrange cat relaxing

Maximum Chill

Professional couch occupier

Cat looking upCat looking up

The Philosopher

Looking up, pondering life's big questions

Cat sittingCat sitting

The Boss

Sitting like a human, judging silently

Full size photo