Adam Peña
I build high-performance systems: accessible, battle-tested, and built to scale.
I've led full-stack development at Cash App and Plaid, building experimentation and data platforms that scale across teams. My work emphasizes performance, accessibility, and systems that hold up under pressure.
English · Spanish · Japanese
Experience
Senior Full-Stack Engineer | Cindersoft | United States
Feb 2025 — Present
- Led technical direction and delivery of SaaS platforms in React/Next.js, Node.js, and Python, spanning shared UI libraries, CI/CD pipelines, and performance optimization.
- Built AWS-backed data sourcing workflows for LLM retrieval, evaluation, and dataset generation for startups backed by OpenAI, Nvidia, and YC.
Lead Front-End Engineer | Cash App (Square) | New York City
Oct 2022 — Feb 2025
- Architected and launched a cross-team marketing experimentation platform for a 60M-user financial app, improving conversion rates by 5% through faster A/B test deployment, real-time metrics, and custom React/Node.js tooling.
- Led full stack performance initiatives, implementing server-side optimizations and front-end tuning to cut page load times by 70% and boost Lighthouse scores by 60+ points.
- Designed and deployed a headless CMS backed by custom API routes and edge functions, powering dynamic content and localization across 10+ regions without engineering support.
- Built and enforced CI pipelines for accessibility testing across marketing and product surfaces, achieving WCAG 2.1 compliance and integrating checks into the deployment process.
Senior Front-End Engineer | Plaid | San Francisco
Aug 2019 — Sep 2022
- Built and maintained shared UI systems and API interfaces across Plaid’s products, used by 1 in 4 U.S. adults, reducing UI bugs by 30% and enabling faster product rollouts.
- Led development of a modular CMS with React, Node.js, and GraphQL, cutting content release time by 60% and enabling self-serve publishing across surfaces.
- Led accessibility audits and full stack remediation across web surfaces, collaborating with backend teams to address semantic data issues and reduce support tickets by 75%.
- Directed Plaid’s engineering apprenticeship program, overseeing mentorship, technical curriculum (React/Node), and logistics; achieved 100% conversion across 20+ apprentices.
Software Engineer | Visibly | Chicago
Sep 2017 — Jul 2019
- Improved onboarding workflows and signup flows, increasing user retention by 25% and boosting first-time purchase conversion by 4%.
- Developed rich, interactive UI components for a proprietary online vision test, contributing to a smoother and more accurate test-taking experience.
Front-End Engineer | ParkWhiz | Chicago
Mar 2016 — Sep 2017
- Redesigned and optimized the core parking widget, increasing performance by 40% and improving booking funnel completion rates.
- Built and shipped a new B2B platform for enterprise partners, reducing client expense report processing time by 35%.
How I work
A few principles I keep regardless of stack or team size.
- Boring is a feature. I reach for the simplest solution that survives real production load. Complexity should be earned.
- Systems, not heroics. The next engineer, including future me, should be able to change the code safely without a walkthrough.
- Performance is a product decision. Latency, layout shift, and responsiveness are user-facing bugs, not infrastructure trivia.
- Tests earn trust. The goal isn't coverage for its own sake; it's the confidence to ship without fear.
- Say the hard thing early. A difficult conversation in week one is cheaper than a surprise in week twelve.
Core stack
Frontend
- React
- Next.js
- TypeScript
- Tailwind CSS
Backend
- Node.js
- Python
- GraphQL
- PostgreSQL
Infrastructure
- Docker
- AWS
- GCP
- CI/CD
Testing
- Jest
- Cypress