William Bertrand

Full Stack Engineer · AI Systems & Agents

Building thoughtful software from idea to production.

Hi, I'm William — a full stack engineer who loves AI agent systems, well-crafted products, and any excuse to be outside watching birds in the mountains.

See my projectsGitHubEmail
Layered misty mountain ridgelines at dawn with a flock of birds flying over pine forest

About

About me

Full-stack engineer with 8+ years of experience building scalable web and mobile applications, with a growing specialty in AI agent systems and LLM-powered product infrastructure. I've been a founding engineer and tech lead across fintech and healthcare, taking products from zero to scale and serving millions of users.

Outside of work, I enjoy hiking, birding, and spending time outdoors. I also build side projects, often exploring language learning, AI, and games.

  • 8+ years

    building web & mobile products

  • Zero to scale

    founding engineer & tech lead

  • Princeton

    B.S. Computer Science, 2017

Skills and technologies

Languages
TypeScriptJavaScriptPythonSwiftJava
Frontend
ReactReact NativeNext.jsAngular
Backend
Node.js / ExpressFlaskREST APIs
AI / ML
AI agent architectureTool-use & memoryAWS BedrockOpenAI APILangChainNLP
Data
PostgreSQLMongoDBMySQL
Cloud
AWSKubernetesCI/CD

Projects

Featured projects

Experience

Work experience

  1. Jul 2024 — Present

    Marble Health

    Founding Engineer

    • Architected and built the core AI agent platform, designing its memory, tool-use, and reasoning layers to support the full patient care lifecycle — from intake through treatment tracking and outcome measurement.
    • Built the infrastructure that lets the agent act across the platform: reading and writing clinical records, surfacing risk signals, and triggering care-coordination workflows.
    • Developed agentic QA pipelines that analyze session transcripts to flag documentation gaps, adherence issues, and coaching opportunities.
    • Shipped AI-powered therapy note drafting serving hundreds of therapists across thousands of appointments, cutting documentation time by more than 50%.
    • First engineering IC hire — established the technical foundation and practices that carried the company through a $15M Series A.

    Tech stack:Next.jsTypeScriptPostgreSQLAWS BedrockLangChain

  2. 2020 — 2024

    Digit (acquired by Oportun)

    Senior Software Engineer

    • Tech lead for the cross-functional team integrating Oportun's lending platform into the Digit app for millions of loan customers.
    • Scaled a new checking account product from 10 users to tens of thousands, handling high-volume financial transactions.
    • Architected critical features for a financial services app serving millions, partnering closely with product and design.

    Tech stack:React NativeNode.jsTypeScriptMongoDBKubernetes

  3. 2019 — 2020

    Augment CXM

    Software Engineer

    • Moved a customer insights platform from daily batch updates to real-time processing.
    • Built data pipelines analyzing hundreds of thousands of support chats daily for live enterprise insights.

    Tech stack:ReactPythonFlaskPostgreSQLKubernetes

  4. 2017 — 2019

    Omniscience Corporation

    Software Engineer

    • Led development of multiple full-stack web applications and a native iOS app.
    • Delivered products end-to-end, from concept to deployment, working directly with sales and external stakeholders.

    Tech stack:AngularJavaMySQLSwift

Contact

Get in touch

I'm open to engineering roles, collaborations, and project ideas. Feel free to reach out.