Concurrency Patterns

Concurrency Patterns

Patterns for safe concurrent programming.

Context

You are choosing a concurrency model. Each has different characteristics.

Domain Context

• Shared Memory: Threads share memory; synchronize with locks
• Message Passing: Actors/processes; no shared memory; communicate via messages
• Async/Await: Cooperative multitasking; single-threaded event loop
• Lock-Free: Use atomic operations instead of locks

Instructions

1. Shared Memory: Use for tightly-coupled code; sync with locks or atomic ops
2. Actor Model: Isolated actors, message-based; scale to many cores easily
3. CSP: Goroutines + channels; lightweight, composable
4. Async/Await: Single-threaded; good for I/O-bound workloads
5. Lock-Free: Complex; use only where locks are provably bottleneck
6. Choose Wisely: Wrong model makes everything harder

Anti-Patterns

• Shared memory + locks everywhere; locks are error-prone
• Message passing when you need shared mutable state; forces unnecessary copies
• Async/await for CPU-bound work; won't help
• Lock-free without deep understanding; very easy to get wrong
• Mixing concurrency models in same codebase; confuses reasoning

Further Reading

• Carl Hewitt, Actor Model (original paper)
• Go documentation on Goroutines and Channels
• Rust documentation on Async/Await