Senior iOS Engineer · Switzerlandhttps://rafalsroka.com/https://rafalsroka.com/posts/swift-concurrency-evolution/https://rafalsroka.com/posts/swift-concurrency-evolution/Concurrency hasn't gotten easier. The sharp edges just moved. Here's what survived from the dispatch_async era, what Combine got right, and where async/await and actors actually help — from someone who's shipped iOS apps at scale across all three.Thu, 14 May 2026 00:00:00 GMThttps://rafalsroka.com/posts/lighthouse-audit-blog/https://rafalsroka.com/posts/lighthouse-audit-blog/I ran Lighthouse against my Astro blog and got a performance score of 56. Three iterations later it was 100. The tools weren't the problem — it was the dev server, the font loading, and a 629KB PNG being used as a 48×48 thumbnail.Tue, 12 May 2026 00:00:00 GMThttps://rafalsroka.com/posts/how-llms-know-when-to-stop/https://rafalsroka.com/posts/how-llms-know-when-to-stop/LLMs don't 'feel' done. They stop because the math tells them to. Here's how.Wed, 06 May 2026 23:00:00 GMThttps://rafalsroka.com/posts/flutter-liquid-glass/https://rafalsroka.com/posts/flutter-liquid-glass/Apple's Liquid Glass isn't just a blur — it's a physically-based, real-time glass simulation that samples the entire render tree behind it. Flutter paints onto a single texture. Those two facts are incompatible.Mon, 12 Jan 2026 00:00:00 GMThttps://rafalsroka.com/posts/llm-context-window-attention/https://rafalsroka.com/posts/llm-context-window-attention/A deep dive into how LLMs manage context through attention mechanisms, and the engineering tricks that push context windows past their quadratic limits.Wed, 20 Aug 2025 00:00:00 GMThttps://rafalsroka.com/posts/swift-opaque-types/https://rafalsroka.com/posts/swift-opaque-types/`some` doesn't just hide a type behind a protocol — it preserves the underlying concrete type identity through the compiler. Here's what that means for performance and why `any` exists alongside it.Sat, 15 Feb 2025 00:00:00 GMThttps://rafalsroka.com/posts/unit-testing-lambda-functions/https://rafalsroka.com/posts/unit-testing-lambda-functions/151 unit tests, no Jest — just Node's built-in runner, tsx, and sinon. The hard part wasn't the test framework, it was understanding module loading order and what the bundler does to your exports.Tue, 08 Oct 2024 00:00:00 GMThttps://rafalsroka.com/posts/swiftui-architecture/https://rafalsroka.com/posts/swiftui-architecture/SwiftUI is not a black box replacement for UIKit. It's a view graph diffing engine that runs on top of UIKit and AppKit. Here's how it actually works.Wed, 05 Jun 2024 00:00:00 GMThttps://rafalsroka.com/posts/swift-copy-on-write/https://rafalsroka.com/posts/swift-copy-on-write/Swift's value types avoid expensive copies until you actually mutate them. Here's how CoW works under the hood.Wed, 10 Jan 2024 00:00:00 GMThttps://rafalsroka.com/posts/nosql-triggers/https://rafalsroka.com/posts/nosql-triggers/NoSQL databases don't have triggers. But their event-driven primitives — streams, change feeds, CDC — let you build the same things with better decoupling. Here's how, and where it hurts.Thu, 20 Jul 2023 00:00:00 GMThttps://rafalsroka.com/posts/aws-lambda-step-functions/https://rafalsroka.com/posts/aws-lambda-step-functions/Lambda and Azure Functions are the easy part. Coordinating them — handling retries, state, error paths, timeouts — is where serverless gets hard. Step Functions solves that, but it's not always the right call.Wed, 15 Mar 2023 00:00:00 GMThttps://rafalsroka.com/posts/ios-testing-best-practices/https://rafalsroka.com/posts/ios-testing-best-practices/Tests are automated. Run often. Preferably on each commit or pull request to quickly catch regressions.Thu, 20 Oct 2022 21:01:00 GMThttps://rafalsroka.com/posts/ios-reference-cycles/https://rafalsroka.com/posts/ios-reference-cycles/Strong reference cycles prevent instances from ever being deallocated, causing a memory leak.Tue, 20 Sep 2022 21:01:00 GMThttps://rafalsroka.com/posts/ios-concurrency/https://rafalsroka.com/posts/ios-concurrency/iOS offers several ways to run tasks concurrently. This article is a short summary of them.Mon, 19 Sep 2022 21:01:00 GMThttps://rafalsroka.com/posts/troubleshooting-graylog-problems/https://rafalsroka.com/posts/troubleshooting-graylog-problems/Common Graylog problems and how to fix them — starting with journal backlog and ElasticSearch flood warnings.Sun, 10 Jul 2022 00:00:00 GMThttps://rafalsroka.com/posts/how-to-switch-aks-clusters/https://rafalsroka.com/posts/how-to-switch-aks-clusters/Quickly change the active Kubernetes context using the Azure CLI.Sat, 09 Apr 2022 00:00:00 GMThttps://rafalsroka.com/posts/purge-soft-deleted-azure-key-vault/https://rafalsroka.com/posts/purge-soft-deleted-azure-key-vault/Azure Key Vault's soft-delete means a deleted vault isn't truly gone. Here's how to purge it completely.Fri, 01 Apr 2022 00:00:00 GMThttps://rafalsroka.com/posts/low-memory-ios/https://rafalsroka.com/posts/low-memory-ios/How crash reporting tools work.Sun, 10 Jan 2016 21:01:00 GMThttps://rafalsroka.com/posts/spritekit-coordinate-system/https://rafalsroka.com/posts/spritekit-coordinate-system/Differences between SKScene and SKNode when it comes to coordinate system in SpriteKit.Tue, 10 Nov 2015 21:01:00 GMThttps://rafalsroka.com/posts/idfa/https://rafalsroka.com/posts/idfa/An alphanumeric string unique to each device, used only for serving advertisements.Mon, 10 Aug 2015 21:01:00 GMThttps://rafalsroka.com/posts/motion-manager-noise-reduction/https://rafalsroka.com/posts/motion-manager-noise-reduction/A way to smooth the accelerometer readings using a Low Pass Filter.Tue, 14 Jul 2015 21:01:00 GMThttps://rafalsroka.com/posts/sounds-in-spritekit/https://rafalsroka.com/posts/sounds-in-spritekit/A couple of tips and tricks and useful code snippets for playing sounds.Fri, 10 Apr 2015 21:01:00 GMThttps://rafalsroka.com/posts/nsrunloop/https://rafalsroka.com/posts/nsrunloop/An event processing loop that you use to schedule work and coordinate the receipt of incoming events.Wed, 09 Apr 2014 21:01:00 GMThttps://rafalsroka.com/posts/mvc-design-pattern-ios/https://rafalsroka.com/posts/mvc-design-pattern-ios/Model-view-controller concept in the iOS world.Sun, 25 Dec 2011 21:01:00 GMT