Jon Stjärnström — Senior Frontend/Fullstack Developer

Stockholm · Consulting · Open for engagements

Senior Frontend/Fullstack Developer — React, Next.js, TypeScript, Node.js

10+ years building high-traffic consumer products, from Sweden's largest real-estate platform to national streaming services.

Get in touch →See the work

01 — About

How he works

10+ years building and maintaining high-traffic web applications, with a primary focus on frontend using React, Next.js, and TypeScript — and full comfort working full-stack, from Node.js backends to auth flows, CMS integrations, and personalization.

Strong focus on performance, SEO, accessibility, and long-term code quality. Works closely with designers and product teams, in both small cross-functional teams and larger product organizations.

Actively uses AI-assisted development workflows — including Claude Code — as part of how he builds today.

02 — Experience

Selected roles

Jun 2025 — Jun 2026
Utbildningsradion (UR)
Senior Developer
Continued development of streaming service urplay.se and UR's in-house CMS, "Edith."
- Built guided onboarding flows for the platform.
- Built a new teacher login using Next-Auth, Keycloak, and Zod.
- Delivered personalized content via a recommendations API (EBU's "Peach").
- Maintained a strong WCAG accessibility focus throughout.
- Used Claude Code throughout for codegen, documentation, and debugging.
ReactSEO & PerformancePlaywrightDockerKeycloakNode.js/ExpressAccessibility (WCAG)Next.jsJestNext-AuthAI-assisted developmentTypeScriptPrismaClaude CodeCI/CDJavaScriptZodKubernetesReact QueryREST APIsSCSS/CSSRedisVite
Sep 2021 — Jun 2025
Hemnet
Senior Developer
Frontend development on hemnet.se, Sweden's largest real-estate platform.
- Contributed to the migration from Rails to Next.js/TypeScript.
- Owned the news articles/advertorials platform and its CMS.
- Built and maintained a component library and design system in Storybook, with a WCAG focus.
ReactPlaywrightSEO & PerformanceDockerContentfulGraphQLWordPressAccessibility (WCAG)JestNext.jsTypeScriptReact Testing LibraryJavaScriptCI/CDRuby on RailsApollo ClientSCSS/CSSDesign SystemsStorybook
Aug 2018 — Sep 2021
KTH Royal Institute of Technology
Developer
Maintained kth.se and internal tools.
- Built and maintained the university's design system.
- Migrated the frontend platform from Inferno.js to React.
ReactJestAccessibility (WCAG)React Testing LibraryJavaScriptSCSS/CSSDesign SystemsStorybookInferno.js

03 — Skills

Grouped by area

Frontend: ReactNext.jsTypeScriptJavaScriptReact QueryApollo ClientSCSS/CSSDesign SystemsStorybookVite
Backend: Node.js/ExpressGraphQLPrismaZodREST APIsRedis
DevOps: DockerVercelNeon (serverless Postgres)CI/CDKubernetes
Auth/Identity: KeycloakNext-Auth
Testing: PlaywrightJestReact Testing LibraryVitest
CMS/Platforms: ContentfulWordPress
Practice: SEO & PerformanceAccessibility (WCAG)AI-assisted developmentClaude CodeSpec driven development