concurrency

Crossbeam provides lock-free data structures and utilities for concurrent programming. The crossbeam-channel crate offers multi-producer multi-consumer channels with better performance than std::sync::mpsc. crossbeam-utils has scoped threads (borrow d

Promises represent eventual completion or failure of asynchronous operations. I create promises with new Promise((resolve, reject) => {}) executor function. The .then() method chains successful results while .catch() handles errors. Using .finally(

Rust's mpsc (multiple producer, single consumer) channels are the safest way to communicate between threads. You send owned values through the channel, transferring ownership to the receiver. This prevents data races because only one thread owns the d

For high-throughput endpoints that serialize JSON or build strings repeatedly, allocations can become a real cost. sync.Pool is a pragmatic tool for reusing temporary buffers without manual free lists. The key is to treat pooled objects as ephemeral:

Grand Central Dispatch (GCD) manages concurrent code execution with dispatch queues. The main queue handles UI updates—I use DispatchQueue.main.async to return to main thread after background work. Global queues provide concurrent background execution

I reached for idempotency the moment retries started duplicating side effects. In Advisory lock helper, I generate a deterministic lock ID and use pg_try_advisory_lock to ensure only one worker owns the critical section; the ensure block always calls

Inventory systems are concurrency systems. Lock the row, verify available quantity, then write the reservation in the same transaction. It’s the simplest correct starting point.

Send means a type can be transferred across thread boundaries. Sync means a type can be shared between threads (&T is Send). Most types are Send + Sync; exceptions include Rc (not Send) and RefCell (not Sync). The compiler uses these marker traits

If multiple admins edit the same record, use lock_version. Rails will raise on conflicting updates, and you can show a friendly “this changed underneath you” message. It prevents subtle lost updates.

Race conditions happen. The correct “find or create” in production uses a unique constraint and a retry on conflict, not a naive check-then-insert. Let the database serialize the race.

SwiftUI's .task modifier handles async operations tied to view lifecycle. The task starts when the view appears and cancels automatically when it disappears, preventing memory leaks. I use .task for data fetching, subscriptions, and long-running opera

Database locks ensure data consistency in concurrent access. I understand lock types—row, table, advisory. Shared locks allow concurrent reads. Exclusive locks prevent all access. Understanding lock granularity prevents contention. Deadlocks occur whe