Carsten Behrens

About

I'm a senior fullstack developer with 7 years of experience shipping products end-to-end for Otto, Gruner + Jahr, and Trusted Shops — and I specialize in backend architecture: REST APIs, event-driven systems, and cloud infrastructure on AWS.

Currently, I'm at Trusted Shops, where I build the backend and cloud infrastructure behind the consumer app for web, iOS, and Android.

I also write about TypeScript and software design on DEV (opens in a new tab), where my articles have reached 46,000+ readers.

I live and work in Hamburg, Germany.

Experience

2024 — Present

Trusted Shops (opens in a new tab) Senior Fullstack Engineer

Drove the Consumer Account platform — a cross-platform application for Web, iOS and Android serving 50,000+ monthly users — from inception to production launch in a team of three, defining the system architecture and owning the AWS infrastructure in Terraform. Designed and implemented a cross-platform push notification system end-to-end, from the AWS (SNS, SQS) and Firebase Cloud Messaging backend to the in-app notification UI in Flutter. Along the way, ran technical interviews and made hiring decisions for the team.
- Dart
- Java
- Flutter
- Spring Boot
- AWS
- Firebase
2021 — 2024

Otto (opens in a new tab) Fullstack Engineer

Served as frontend lead in a team of 5 engineers on OTTO Partner Connect, a partner platform serving 2,000+ partners on Spring Boot and Vue.js — driving technical decisions, code review standards, and a JavaScript-to-TypeScript migration that lifted test coverage from 43% to 84%. Built a configurable form builder that let internal teams launch new partner services in days instead of weeks, and eliminated manual regression testing by architecting an end-to-end API test suite with Cucumber and Rest Assured — increasing deployment frequency from 1 to 4 per week.
- Java
- Spring Boot
- AWS
- TypeScript
- Vue.js
2019 — 2021

Gruner + Jahr (opens in a new tab) Software Engineer

Built the multi-tenant Node.js server powering Gruner + Jahr's biggest editorial sites, including stern.de and brigitte.de — rendering pages server-side for 6+ million monthly visitors. Led web performance optimization across all properties, introducing Real User Monitoring and collaborating with ad agencies on Core Web Vitals — cutting Largest Contentful Paint by 35%.
- Node.js
- Express
- TypeScript
- Handlebars

Skills

I'm a backend-focused fullstack developer with 7 years of experience building applications end-to-end.

Throughout my career, I've worked across the stack — from Spring Boot and Node.js to React, Vue, and Flutter. Frameworks constantly evolve, so I focus my energy on the software design principles underneath them rather than memorizing syntax. That foundation lets me adapt quickly and choose the best tool for the problem at hand.

“It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.”

— Abraham Maslow

In my last two roles, applying that philosophy meant taking features the whole way: setting up the infrastructure in Terraform, building the service in Spring Boot, shipping the UI in React or Flutter.

The backend is where I go deepest. I love designing services and the infrastructure they run on — REST APIs, event-driven messaging on SNS and SQS, ECS services and Lambda functions provisioned with Terraform — and I care about keeping them reliable, observable, and maintainable long after the first release.

Technologies I've worked with, past and present

TypeScript
Vue.js
React
Node.js
Express
Java
Spring Boot
GraphQL
Flutter
Dart
Firebase
MongoDB
MySQL
PostgreSQL
DynamoDB
OpenSearch
Hibernate
Grafana
AWS
Docker
Terraform
GitHub Actions
Cypress
Jest
Cucumber
CircleCI

Projects

Boom Bap App (opens in a new tab) Sampler & Step Sequencer

A browser-based sampler, step sequencer, and drum machine. Load samples, slice them up, program beats on a grid, and hear the pattern play back in real time — all triggered and scheduled in the browser.
- TypeScript
- React
- Tone.js
- WaveSurfer
- Zustand
- Tailwind