James Paik

I'm an entrepreneur with a technical background.

  • Currently I'm a Staff Software Engineer at Headway.
  • On the side, I run a web development business, Zinnia Development.
  • I also enjoy developing games as a hobby and run Cosinic.

I focus on building beautiful and scalable applications that both the development team and the end users are satisfied with. I tend to explore new technologies and build projects with them to expand my boundaries in this seemingly endless field.

Experience

Headway

Sep 2026 - Present

Staff Software Engineer

    Klaviyo

    2022 - 2026

    Lead Software Engineer

    Feb 2024 - Aug 2026

    • Led engineering for Flows & Automations, the company's automated marketing sequences, and Klaviyo Composer, the company's AI marketing agent. Designed the chat-to-subagent orchestration architecture and took the product from concept to launch in under 2 months.
    • Co-architected Encoded Flows, the DAG-based JSON data model that now serves as the source of truth for Klaviyo's automation engine, defining its core design principles and evolving its schema to power the public APIs and AI/LLM products.
    • Shipped Scheduled Flows from design through GA with SLOs and monitoring; reached 11% adoption across all automation launches during Black Friday within weeks of release.
    • Rebuilt cross-product analytics exports: multi-day, 2M-profile enterprise exports now finish in 1-2 hours (90% faster) at ~10% of the prior compute cost.

    Senior Software Engineer

    Sep 2022 - Feb 2024

    • Rebuilt Flows analytics on a unified metrics layer: P99 latency from 12s down to 0.7s and up to 100× faster for enterprise accounts, eliminating timeout failures and cutting analytics bug reports by over 70%.
    • Lead engineer on the ground-up flow builder UI rebuild, shipped to all customers ahead of Black Friday; component architecture let 4+ engineers build in parallel.
    • Eliminated an entire class of customer-facing failures by converting flow cloning from a blocking synchronous operation into an asynchronous pipeline.
    • Hardened the real-time price-drop event pipeline for Black Friday peak traffic: 50–70% faster event queries plus a new caching layer, delivering a stable peak season.

    Actovia

    2016 - 2022

    Lead Full Stack Developer

    Jan 2020 - Sep 2022

    • Collaborated and led a team of engineers at Actovia while coordinating with the company’s leaders to implement and execute new ideas.
    • Developed full stack applications using Vue.js/Nuxt.js with Typescript for frontend and .NET Core with C# and Node.js with Typescript for backend. Used SQL Server and PostgreSQL for databases.
    • Worked closely with the marketing team to create a demo version of the web application with dynamic SEO and dynamic sitemaps for property searches with automated sign up subscriptions to create a new acquisition workflow.
    • Implemented CI/CD practices using Gitlab CI/CD and Github Actions to deploy dockerized applications to GCP and DO.

    Lead Front End Developer

    Aug 2016 - Dec 2019

    • Led the UI/UX redesign and development of Actovia's applications. Designed and developed the applications using HTML5, SCSS, Javascript, jQuery and Vue.js with the .NET Framework, ultimately increasing acquisition and retention rates by 150%
    • Implemented E2E testing with Cypress and integrated with Jira which led to a significant decrease of bug fix requests from users.
    • Developed and maintained an internal custom CRM to work specifically with the Actovia Application.
    • Streamlined workflow with Task Runners (Gulp & Webpack), SCSS, Babel and new ES JS standards with documentation for the team.

    Zinnia Development

    Jul 2014 - Present

    Founder & Lead Developer

    • Incorporated Zinnia Development LLC for my hobby on creating websites for small businesses officially in 2019.
    • Designed and developed over 30 small business websites and web applications since inception, working directly with small business owners.
    • Lowered hosting costs and downtime for small businesses by over 90% from their previous setup by utilizing serverless and cloud computing solutions and ensured reliability for these websites.

    Trade Trendy

    Sep 2015 - Dec 2016

    Co-Founder & Technical Lead

    • Lead the development of Trade Trendy to revolutionize the online clothing market. Trade Trendy was an online marketplace to trade used clothing, shoes, and accessories.
    • Developed the web application using Ruby on Rails for the backend with jQuery and Bootstrap for the frontend.
    • Produced a scalable architecture as the user base grew from tens to thousands of concurrent users using AWS EC2 auto scaling groups and ELB.
    • Conducted weekly sprint goals to meet our feature log with consultant developers.

    Projects

    ONUW.io

    Dec 2018 - Dec 2020

    Creator

    • ONUW is an online multiplayer game based on a board game.
    • Used Node.js running Express.js for views and routing with Socket.io for real time interaction.
    • Running on a DO Ubuntu droplet with Nginx as reverse proxy and PM2 for management.
    • As of 2022, there are around 200 players around the world playing daily.

    GPA For Me

    Apr 2016, 2020

    Creator

    • Created using Vue.js + Nuxt.js with Auth0 authentication and serverless deployment with a serverless MongoDB database to store user information.
    • Old Version: To explore AngularJS, I created a GPA Calculator using Angular2.
    • It calculates GPA in real time with both semester and cumulative GPA scores. Users can choose from the three different GPA scales as well.
    • Every season during the end of the semester, there are over 5,000 students that use this to calculate their GPA and hope for the best.

    Course Sniper

    Dec 2015

    Front End Developer

    • Designed and developed the front end of the web application that is used by over 7,000 Rutgers students every semester, assisting them with class registration.
    • Rewrote the frontend to be responsive and user friendly

    RU Direct

    Apr 2015

    Front End Developer

    • Developed an android app for the bus system at Rutgers University during HackRU 2015.
    • Continued to maintain the project resulting in over 10,000 Rutgers students using it daily.
    • As of 2019, Rutgers changed their services to TransLoc, resulting in the shutdown of this app.

    Favorite Tech

    • JavaScript
    • Typescript
    • React
    • Vue.js
    • Python/Django
    • Node.js
    • MySQL/PostgreSQL
    • Redis
    • Claude Code/Codex
    • Anthropic/OpenAI APIs
    • PydanticAI/LangChain
    • AWS

    Connect with me