Arek Holko

About Me

Hi! I'm Arek Holko, an iOS engineer in Warsaw, Poland. You can subscribe to my newsletter to stay updated.

You can reach me via:

Indie Apps

Speed reading trainer

I always wanted to read more and read faster. That's why I created Outread. I implemented the whole app by myself, made many mistakes and learned a lot in the process. Liked by the users (4.7-star rating) and featured on the front page of the App Store.

Smart unit converter

Being born in a metric-based and constantly encountering imperial units I decided to tackle the unit conversion problem. Uniter lets you quickly convert units of measure in text, on websites in Safari, and live on the camera view.

Selected Client Work

Smarter email client

I led iOS development starting from early beta through reaching market leadership, building a 3-person distributed mobile team along the way. I engineered solutions across the whole product: from a rewrite of a low-level persistence layer achieving 10x better performance to high-level product planning and monetization efforts through subscriptions.

Interactive guitar teacher (watch the video 📺)

I was mostly responsible for Chord Trainer (in the video above), everything from a flexible model up to a custom animation engine based on POP and Core Animation. Created by the team of eight engineers split into two countries. Featured on the App Store in Best New Apps.

Art Intelligence (defunct)

Platform for promoting art through apps

We built a flexible system for creating apps about art. As a lead developer, I created some technically-challenging parts of UI and helped bring the project to completion despite heavy time constraints.

OUTlife (defunct)

Social network for LGBTQ

I was focused on two parts of the app: model (based on Core Data) and the main feed infrastructure (based on ComponentKit and immutable models).


I find that writing helps me come up with better solutions to problems I think about. My articles are often featured by iOS publications, such as iOS Dev Weekly, NatashaTheRobot and iOS Goodies.

Here are some articles that you should start from:

See all articles.

Open Source

Over the years, I built many small, focused open source projects used in total by thousands of developers. Here are my current favorites:

See more on my GitHub profile.


I've been programming since high school. To keep my horizons broad, I got degrees in Mathematics and Finance.

I was fortunate enough to publish, in a top computer science journal, a research article: “Epidemiological modeling with a population density map-based cellular automata simulation system”.