Andriy Druk

I’m a software engineer and technical writer focused on building high-quality mobile and cross-platform software. I’ve spent the last eight years at Readdle working on Spark Mail - one of the most popular email clients in the world, running on iOS, Android, Mac, and Windows.

Android Engineering Lead at Spark (2017–2024)

I led the Android engineering team at Spark, where my main challenge was bringing an iOS-born email client to Android without rewriting the entire codebase. We chose Swift as the cross-platform language and I built the open-source Swift Android Toolchain - seven repositories covering everything from a patched Swift SDK to JNI code generation and NDK bindings.

Under my lead, the team shipped Spark for Android with its entire business logic written in Swift - email sync, calendars, and later AI features - all shared with iOS from a single codebase. We evolved from a forked compiler to tracking upstream Swift 6.x with three architecture targets.

This work grew beyond Readdle. I became a member of the Swift on Android Working Group and contributed to the official Swift SDK for Android published on swift.org. Together with the Swift core team, Google, and the broader community, Swift on Android evolved into an officially supported platform in the Swift ecosystem.

AI Foundation Lead at Spark (2024–present)

I transitioned to lead Spark’s AI/ML team, responsible for all AI-powered features in the email client. My team shipped the AI Assistant - including a fully local RAG pipeline running on all four major platforms (iOS, Android, Mac, and Windows). Building on-device retrieval-augmented generation that works across such different hardware and OS constraints was one of the most technically rewarding challenges I’ve tackled.

Beyond shipping features, I led an architecture overhaul of Spark’s agent system to support rapid model switching. We’re continuing to explore new ways AI can make email smarter and more efficient.

Open Source & Community

I have long roots in the developer community and open source:

• Swift Android Toolchain - enabling Swift to compile and target Android, with build tools, JNI bridging, and NDK bindings.
• LM Playground - an Android app for running large language models locally on device.
• Bonjour Browser - a network-service-discovery utility for developers (and the related RxDNSSD library for Android).

If you’d like to chat about Swift on Android, mobile UX, cross-platform development, or applied AI - I’d love to connect.

• Contact me: [email protected]
• Follow me: @andriydruk
• Github: github.com/andriydruk