Open to opportunities

Kamil Takahashi

@kamiltakahashi

Senior Frontend Developer building scalable React/TypeScript SaaS with performance, accessibility, and compliance-first UX.

Poland

Message

What I'm looking for

I’m looking to build React/TypeScript products where performance, accessibility, and compliance matter—shipping auditable fintech/health interfaces, mentoring engineers, and improving Core Web Vitals through thoughtful architecture and tooling.

I’m a senior frontend engineer with 9 years building scalable SaaS applications for fintech, health tech, and enterprise platforms. I specialize in React and TypeScript-first development, focusing on financial workflows, payment systems, and compliance-sensitive product surfaces.

At Mercury, I architected and shipped a multi-currency contractor payout dashboard using React with Next.js and TypeScript, leveraging server components and streaming SSR for high-throughput ledger queries. I redesigned contractor onboarding by integrating third-party KYC/KYB verification, cutting median completion time from 9 minutes to under 2, and I sustained Lighthouse scores above 95 using code-splitting, lazy-loaded routes, and Lighthouse CI in GitHub Actions.

I also improved real-world speed by reducing First Contentful Paint from 2.1 seconds to 480 ms via the Next.js App Router and React Server Components, and I built an internal payments-provider component library with 80+ Storybook references. Across teams, I’ve delivered accessible, auditable UI systems—fixing performance issues like excessive re-renders, addressing a SEV-2 memory leak, and mentoring engineers through frontend architecture reviews aligned with SOC 2 audit requirements.

Experience

Work history, roles, and key accomplishments

Current

Senior Frontend Developer

Current

Mercury

Mar 2022 - Present (4 years 3 months)

Architected and shipped a multi-currency contractor payout dashboard using React, Next.js, and TypeScript, leveraging server components and streaming SSR to keep ledger-driven views responsive. Improved contractor onboarding completion time from 9 minutes to under 2, sustained Lighthouse scores above 95, reduced FCP from 2.1s to 480ms, and cut JS bundle size by 35%, while fixing a SEV-2 memory lea

React Next.js TypeScript React Server Components Streaming SSR Tanstack Query Lighthouse CI Sentry Storybook

Frontend Developer

Dialogue

Jan 2020 - Feb 2022 (2 years 1 month)

Owned end-to-end multi-tenant appointment-scheduling UI in React with Next.js, shipping TanStack Query optimistic updates and offline-friendly write queues for unreliable networks. Reduced Largest Contentful Paint from 1.8s to 320ms, built UI integrations for 30+ clinic/lab record views against HL7 and FHIR contracts, and implemented role-based patient data masking with audit logging to support co

React Next.js Tanstack Query Offline Queueing HL7 FHIR LaunchDarkly Sentry

Frontend Developer

Netguru

Nov 2017 - Jan 2020 (2 years 2 months)

Built React UI components and shared widgets for the catalog and merchandising platform using JavaScript with Webpack and Babel, translating design handoffs into accessible reusable interfaces. Increased test coverage from 45% to over 85% using Jest and React Testing Library and resolved a hydration mismatch that caused intermittent layout shifts during nightly catalog re-imports.

React JavaScript Webpack Babel Jest React Testing Library SSR Hydration Debugging Accessibility

Junior Frontend Developer

HacarUS

Apr 2016 - Oct 2017 (1 year 6 months)

Built interactive React applications for course content delivery, improving student engagement from 45% to 72% through improved form UX and state management. Implemented Redux and TanStack Query to cut redundant API calls by 65% and created a reusable 50+ component Storybook library that reduced feature development time by 50%.

React Redux Tanstack Query Storybook