Aaron Hammer

Full Stack Developer, Side Project Enthusiast, and API Consumer


Work Experience

Square - Block

October 2022 - Present
Full Stack Software Engineer L4
  • Designed and led several projects for Square Payment Links on a 9-person team using Golang, PHP, Typescript, and Vue that managed over $2.2 billion in processing volume, growing 54% YoY for 2023.
  • Rebuilt Square Payment Link’s tipping feature to let over 1 million sellers customize tip percentages, support their local currencies, and to provide more localized tipping percents as defaults.
  • Created new observability standards by migrating the team’s observability stack to Datadog, introducing anomaly alerts, better monitoring dashboards, front-end metric alerting, and automatic API acceptance testing.
  • Led the migration of all tier-1 services that manage public Square Payment Links’ API and our other internal services and databases from on-prem to AWS infrastructure using Terraform.
  • Created the buyer-side flow for Square’s restaurant QR code checkout experience, bringing over $70 million in processing volume for Square Payment Links’ MoM.

Formerly Rally Health - Optum Digital / UnitedHealth Group

July 2021 - October 2022
Full Stack Software Engineer II
  • Contributed with an 8-person Scrum team to a React front-end and Scala microservice back-end for a highly visible UHC healthcare client dashboard that’s accessed by over 50 million customers worldwide.
  • Led and rapidly implemented the front-end requirements for a SSO redirect on myUHC to enable over 26 million customers to receive free COVID-19 tests by weeks end to comply with federal mandates.
  • Drove a performance initiative to improve UX. I reduced our max bundle from 1.62MBs to 495KBs and slashed FCP by 0.4 seconds through lazy-loading, bundle-splitting and concurrent rendering.
  • Spearheaded the front-end work for a domain unification effort on myUHC for all lines of business, resulting in a decrease in domains from 6 to 1, leading to greater customer and developer clarity.
  • Contributed with a dedicated team to migrate myUHC from AngularJS to ReactJS. Removing AngularJS from our bundle led to a drop in bundle sizes by 30% and shrunk page load time by ~15%

Clearview Social

August 2019 - July 2021
Full Stack Software Developer
  • Engineered a web and mobile React/ Expo React Native app with a Node Express backend with an Agile 5-person team for a consumer facing SaaS app.
  • Reduced React bundle size ~12% with tree shaking, package pruning, and using size optimized library
  • Led an initiative to reduce database load and API response times by introducing a Redis cache aside strategy on top of our RESTful API Node.js backend. Cache hits approached 85% on some common endpoints.
  • Modeled and created the AWS infrastructure and design docs for a scalable serverless image caching API that returns images in a specified dimension and image format while caching alternative formats. This decreased total image requests transfer size on some pages by over 80%.

Clearview Social

May 2018 - August 2019
  • Participated in creating a newly published Android and iOS app created with React Native, Redux, and Expo
  • Maintained and contributed to a SaaS web app built with React, Node.js, Express, Webpack, and Sass
  • Developed and renovated unit tests and snapshot tests with Mocha, Chai, and Jest across both mobile and web, with an average of 92% coverage across all branches
  • Engineered queries using Sequelize and raw SQL for MySQL database hosted on AWS's RDS



October 2023 - Present
To be released
- Owner and Creator
  • Helps users find the best deals on video games across multiple stores. Built with Solid.js, TailwindCSS, and Golang.


January 2023 - October 2023
- Owner and Creator
  • Service that lets users share costs with friends and family with one-time and subscription payments. Built with React Server Components, TailwindCSS, MySQL, and Stripe for payment processing.