iOS at Scale: Swift Concurrency

You know what an actor is. You've used async/await. You've probably even shipped Task and TaskGroup in production.

This book isn't an introduction to any of that. It's what happens after you know the syntax — the ten specific ways Swift's concurrency model quietly breaks in real apps, explained clearly enough that you stop making these mistakes instead of just memorizing that they exist.

Every topic follows the same shape: the assumption that seems reasonable → the bug that assumption causes → the fix → a rule of thumb you'll actually remember → the follow-up most people miss.

What's Inside — 10 Topics

1. Actor Reentrancy — why an actor doesn't make a multi-step operation atomic across an await
2. Priority Inversion — why higher task priority doesn't always mean faster, and the one case where it structurally can't
3. Sendable & Isolation Boundaries — why @unchecked Sendable is a promise the compiler stops checking, forever
4. Bridging Legacy Callback SDKs — the continuation contract most wrappers silently violate
5. Cancellation — why it's a signal your code has to check, not a stop that happens automatically
6. MainActor & UI Ordering — safe from races doesn't mean safe from the wrong update winning
7. AsyncStream & Backpressure — what happens when your producer is faster than your consumer
8. Global Actors & Legacy Sync Code — how to bridge async-first design into code that can't await
9. Testing Concurrent Code — why a passing test usually proves less than you think
10. Migrating a GCD/Combine App — an interop strategy that doesn't multiply your bug surface

Who This Is For

• iOS engineers who've adopted Swift concurrency and want to actually understand its sharp edges, not just its syntax
• Anyone who's shipped an actor and had a nagging feeling they didn't fully reason through every suspension point
• Engineers preparing for senior/staff-level technical discussions where "I used an actor" isn't a complete answer
• Anyone migrating a GCD or Combine codebase who wants a real strategy, not just ad hoc wrapping

What's Included

• 📖 Full book — PDF + ePub, all 10 topics
• 💻 Every code example as a runnable Swift snippet
• 📊 Diagrams for every topic where a picture genuinely explains it faster than prose
• 🔄 Free lifetime updates as new topics are added