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I build stuff.

Hi, I'm Perttu Lähteenlahti — a developer and designer based in Finland. I've spent the last decade designing and building digital products, from mobile apps to web platforms. I also won 40+ hackathons along the way.

Currently, I work as a Senior Developer Advocate at RevenueCat, where I help developers build and monetize their apps. My focus is on React Native, cross-platform development, and making in-app purchases less painful. You can read more about me, or see what I'm up to now.

What I write about

I write practical, production-focused guides about React Native, iOS and Android development, mobile performance, and app monetization — especially subscriptions and in-app purchases. Most articles are based on real issues I've hit while building and shipping apps in production.

Perttu at React Native Live conference
Perttu speaking at a conference
Perttu at App.js conference
Perttu at a hackathon event
Perttu operating a crane

Articles & Tutorials

I write about React Native development, mobile app monetization, in-app purchases, and lessons learned from building products. Here are some of my recent posts.

Cover image for How to Invoice Apple for App Store Proceeds (with VAT)

How to Invoice Apple for App Store Proceeds (with VAT)

Apple hands you a CSV, not an invoice. Drop your App Store Connect financial report below and instantly generate the self-issued invoice and itemized report your accountant needs — one PDF, entirely in your browser.

Recent Talks

  1. How to make money with your Flutter app

    FlutterKaigi 2025

  2. Building & monetizing a React Native app for three platforms in 20 minutes

    React Advanced London 2025

  3. Why React Native apps make all the money

    React Conf 2025

See all talks

Work

  1. RevenueCat logo
    Company
    RevenueCat
    Role
    Senior Developer Advocate
    Date
  2. Fenrir Digital logo
    Company
    Fenrir Digital
    Role
    Founder
    Date
  3. Noice logo
    Company
    Noice
    Role
    Senior Mobile Developer
    Date
  4. Veri logo
    Company
    Veri
    Role
    Product Lead
    Date
  5. Mavericks logo
    Company
    Mavericks
    Role
    Senior Software Engineer
    Date
Download CV

Projects

  1. Nyxo icon

    Nyxo

    Sleep tracking and coaching app with multi-device sync.

  2. Netli.fyi icon

    Netli.fyi

    React Native app for managing Netlify sites.

  3. konkurssit.live icon

    konkurssit.live

    Finnish bankruptcy tracking app with real-time data.

See all projects