Hi, I’m Julien Karst
Tech Lead & Developer

I help startups and businesses build exceptional digital experiences with modern web technologies.

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120+ Projects Completed

10+ Years Experience

I’m a Tech Lead & Full-Stack Developer based in Nancy, France

With over 10 years of experience in web development, I specialize in building high-performance, scalable applications using modern technologies like React, Node.js, and TypeScript.

I’ve worked with startups and established companies to deliver exceptional digital experiences that drive business growth and user engagement.

Name:

Julien Karst

Email:

hello@julienkarst.com

Location:

Paris, France

Availability:

Open to opportunities

Trusted Code

Open Source Contributions

Companies and projects powered by my code

Performance Metrics

Proven Excellence

Delivering measurable results through technical expertise and strategic innovation.

Projects Delivered

A+

Code Quality

On-Time Delivery

Engineers Mentored

My Process

A proven methodology for delivering exceptional results

Step 1

Discovery

Understanding your business, goals, and requirements to create a solid foundation.

Step 2

Planning

Developing a strategic roadmap with clear milestones and deliverables.

Step 3

Execution

Building your solution with regular updates and opportunities for feedback.

Step 4

Delivery

Launching your project with thorough testing and ongoing support.

Ready to start your project?

Get Started

Technologies I work with

Objective-C

Swift

Android

iOS

Postgres

MongoDB

Web3

Git

React-Native

Next.js

Objective-C

Swift

Android

iOS

Postgres

MongoDB

Web3

Git

React-Native

Next.js

Services

Expert development solutions that accelerate your business growth

Backend

Designing resilient, scalable back-end systems that power your products and grow with your traffic.

REST & GraphQL APIs

Microservices and event-driven architecture

Database schema & performance tuning

Observability, logging, monitoring

ML-based demand forecasting for scaling

AI-driven data validation & anomaly detection

Learn more about Backend

Code Reviews & Audits

Comprehensive analysis of your codebase to identify issues, improve quality, and implement best practices.

Code quality assessment

Security vulnerability detection

Performance bottleneck identification

Refactoring recommendations

Infrastructure-as-Code review

Dependency & license compliance check

Learn more about Code Reviews & Audits

Mobile development

Crafting high-performance iOS & Android apps—native or cross-platform—tailored to your business goals.

Swift / Kotlin & React Native

App Store & Play Store deployment

UI / UX implementation

Automated CI/CD

AI-driven features

Push notifications & in-app messaging

Performance & Animations

Learn more about Mobile development

Product & UX Design

Crafting intuitive, visually engaging interfaces that delight users and achieve business goals.

User research & personas

Wireframing & prototyping

Design systems & style guides

Accessibility & WCAG compliance

AI feature inside product

Predictive UX analytics via ML

Learn more about Product & UX Design

Technical Consulting

Providing expert advice on technology stack selection, architecture design, and development workflows

Technology stack assessment

Architecture planning

Development workflow optimization

Technical documentation

Architectural decision

AI-driven stack recommendations

Learn more about Technical Consulting

Web Development

Custom web applications and websites built with modern technologies and best practices

React & Next.js Development

TypeScript Implementation

Responsive Design

SEO Optimization

Performance Optimization

Security Best Practices

Progressive Web Apps (PWA)

E-commerce Integration

Learn more about Web Development

Latest Insights

Thoughts on technology, development, and digital innovation

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How to display time ago from a date in Swift

Two approaches to display relative time in Swift: the built-in RelativeDateTimeFormatter for Swift 5.1+ and a manual implementation for older versions.

6/24/2020

5 min read

swiftiosdate-formatting

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