Actor Model — Concurrency Without Shared State

Why it matters

Actor model changes how concurrent programming works. Instead of protecting shared state, actors avoid it. Simpler to reason about and inherently scalable.

The architecture

Actor: unit with private state and mailbox. Processes messages one at a time.

Messages: async. Sender doesn't wait for receiver.

How it works end to end

Mailbox: queue of pending messages. Actor processes one at a time — no concurrent modification of its state.

Supervision: parent actors restart failed children. 'Let it crash' philosophy.

Location transparency: actor address same whether local or remote.