Rex Lin

Builder.

Now

Heads down on a startup and a few side projects. More here when they're ready. If you're curious in the meantime, email works.

Before

Five and a half years at Affirm as a machine learning engineer, 2019 to early 2025, across the ML platform, computational finance, and portfolio ML teams. A few things I'm glad shipped:

Profitability-based underwriting

Portfolio ML, 2023 to 2025

Architected an underwriting decision system based on loan profitability, with a proprietary online model that generated over $8.2M in contribution margin. Led a pod of five engineers across four teams for the next phase.

Patented loan pricing engine

Computational Finance. US patent US-20240104645-A1, issued March 2024

Simulation-based pricing optimization that cut a week-long analyst workflow to six hours.

Online feature store

ML Platform, 2019 to 2020

Horizontally scalable feature serving on AWS Aurora and gRPC, serving over a million features in production.

Earlier

Stereocilia imaging research

LBNL. stereocilia and cnn_segmentation

Segmented actin filaments in cryo-EM 3D tomographic data, then helped automate the segmentation with CNNs.

UC Berkeley

2014 to 2018

Dual B.A. in Data Science and Molecular and Cell Biology.

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