Sebastian Boldt - Mobile Application Engineer

What I Do

Clean architecture, modular design, maintainability.

I build iOS apps with a focus on these principles.

Architecture & Modularity

I’m comfortable working with different iOS architectures like MVVM, VIPER, and more traditional patterns, but today I mostly use a Redux-style approach with The Composable Architecture (TCA) and the Point‑Free ecosystem. I use Swift Package Manager to create clear boundaries between modules so features stay reusable and easy to slice out. Regardless of the pattern, I focus on clear dependency injection so that code stays modular, testable, and easy to evolve.

TCA SPM MVVM MVC VIPER Clean Architecture

Framework Knowledge

I work daily with SwiftUI and have extensive experience with UIKit on large-scale projects. Over the years I’ve worked with frameworks like AudioKit, StoreKit, CloudKit, WidgetKit MapKit, Core Data, and also things like the iOS Accessibility APIs. I can also work with Objective-C when needed for maintaining and extending legacy codebases, and I adapt quickly to new frameworks and domains.

Swift SwiftUI UIKit Objective-C

Team Collaboration & Mentoring

I mentored developers and presented on iOS topics. I've worked in large international teams with mono-repos and multi-repo setups, as well as smaller local teams. I've also worked with CI/CD tools like Xcode Cloud, Bitrise, and Jenkins to automate the build and release process.

CI/CD Xcode Cloud Bitrise Jira & Scrum

Agentic Coding

I work with AI coding tools like Claude Code, Cursor, and Codex to accelerate development, while using Skills, MCP Servers. My years of native iOS experience help me keep away the "Slop-Layer" and keep AI-generated code maintainable.

CursorCodexSkills

Work

Where I've worked.

10/2022 – Present

Lead Developer Mobile (iOS) · Aviv

SeLoger iOS app ~3.5 yrs ★4.7 · 155k+ Reviews

04/2016 – 10/2022

Software Engineer Mobile (iOS) · Immowelt/Immonet

Immowelt iOS app ~6.5 yrs ★4.6 · 150k+ Reviews

02/2015 – 03/2016

Mobile Application Developer (iOS) · Fashionfreax

~1 yr

08/2013 – 10/2014

Software Developer (C++ / QT / iOS / Android) · IPT Wismar

~1 yr

Education

Master's & Bachelor's in Multimedia Engineering, Hochschule Wismar

Microprocessor technology, image processing, computer graphics, audio, system programming, networking, application development.

What others say

What others say.

Kevin Hirsch

Principal Engineer · Aviv

“Sebastian is always there to help on every topic (being humble, open-minded and approachable), making sure that the whole iOS community is aligned, tackling transversal problems for developers or the products we build, aiming to simplify the work of all our iOS developers so they can deliver great results on the audacious objectives we have at Aviv, setting ourselves up for success! Thanks Sebastian.”

More feedback from colleagues will be added here over time.

Projects

Apps I've built in my spare time.

HabitBe, Pianoo, and more.

HabitBe

The habit tracker for minimalists.

Active★4.7 · 351 Reviews

A simple weekly habit tracker. No fancy features, just tracking what matters. Built with TCA, Core Data, CloudKit, SwiftUI.

habitbe.app →

Pianoo

Chords. Scales. Progressions.

Active

A music theory app for chords, scales, and progressions. Simple and useful for writing songs or practicing.

pianoo.app →

More projects

Jelly

Open-source library for animated view controller transitions in UIKit.

Swift UIKit ★2.5k+ stars

Open Source

Soundrocket

My first App Store release (2015), a SoundCloud client I stopped after their public API was shut down. The project is now private but still an important part of my journey.

Objective-CUIKit

Inactive

Blog

Articles on iOS development.

I haven't written new posts recently—focusing on building apps instead.

IGListKit in 10 Minutes (2018) RxSwift in 10 Minutes (2017) iOS Code Signing (2016)

Mobile Application Engineer
from Hamburg.