+-----------------------------------------------------------------------------------------+
|                  Actor Model Framework Architecture Matrix (2026)                       |
+-----------------------------------------------------------------------------------------+

ELIXIR / ERLANG OTP (The Native Pioneer & Gold Standard)
- Isolation Model: Lightweight BEAM process-level isolation (Each process has its own private Heap & GC!).
- Supervision: Built directly into language runtime with 'one_for_one' and 'rest_for_one' strategies.
- Best for: Telecom, massive chat (Discord/WhatsApp), live IoT, fault-tolerant distributed platforms.

APACHE PEKKO (The Open-Source JVM Standard - Akka Successor)
- Isolation Model: Heap encapsulation within JVM; mature ActorSystem clustering.
- Best for: Enterprise Java/Scala backends migrating from commercial Akka licenses.

PROTOACTOR (High-Throughput Go & .NET Engine)
- Isolation Model: Context-aware goroutines with lock-free ring buffer mailboxes.
- Superpower: Virtual Actor pattern with ultra-fast serialization and cross-language clustering.
- Best for: Cloud-native Go microservices requiring millions of messages/sec throughput.

RUST ACTORS (Kameo / Actix / Ractor - Zero-Cost Safety)
- Isolation Model: Compile-time memory safety via Rust Ownership and 'Send + Sync' traits!
- Best for: Ultra-low-latency financial HFT matching engines, embedded systems, robotics.

+-----------------------------------------------------------------------------------------+
|                  Shared-Memory Locking vs Actor Model Concurrency                       |
+-----------------------------------------------------------------------------------------+

SHARED-MEMORY LOCKING (Mutex Contention & Deadlocks):
[Thread 1] ───\
[Thread 2] ────> [MUTEX LOCK: sync.Mutex] ───> [Shared Balance Struct: $5,000]
[Thread 3] ───/
* Contention: Threads block each other; Deadlock risks; Process crashes on panic!

ACTOR MODEL CONCURRENCY (Lock-Free Message Passing):
[Sender 1] ──(Deposit $100)──>  +---------------------------------------+
[Sender 2] ──(Withdraw $50)──>  | ACTOR MAILBOX (FIFO Queue)            |
[Sender 3] ──(Get Balance)───>  +-------------------+-------------------+
                                                    │ (Sequential processing)
                                                    ▼
                               +----------------------------------------+
                               | ACCOUNT ACTOR (Private State: $5,050)  |
                               | * Processes 1 message at a time in RAM!|
                               | * ZERO LOCKS! ZERO RACE CONDITIONS!    |
                               +----------------------------------------+

# lib/order_book/engine.ex
defmodule OrderBook.Engine do
  use GenServer, restart: :transient
  require Logger

  # 1. Client API
  def start_link(symbol) do
    GenServer.start_link(__MODULE__, symbol, name: via_tuple(symbol))
  end

  def place_order(symbol, order) do
    GenServer.call(via_tuple(symbol), {:place_order, order})
  end

  defp via_tuple(symbol) do
    {:via, Registry, {OrderBook.Registry, symbol}}
  end

  # 2. Server Callbacks & Private Actor State
  @impl true
  def init(symbol) do
    Logger.info("📈 [ACTOR SPAWNED] OrderBook Engine initialized for #{symbol}")
    {:ok, %{symbol: symbol, buy_orders: [], sell_orders: [], total_volume: 0}}
  end

  @impl true
  def handle_call({:place_order, order}, _from, state) do
    # Simulated Order Execution (100% Sequential within this Actor!)
    new_volume = state.total_volume + order.amount
    new_state = %{state | total_volume: new_volume}
    
    {:reply, {:ok, %{status: :filled, new_volume: new_volume}}, new_state}
  end
end

# lib/order_book/supervisor.ex
defmodule OrderBook.Supervisor do
  use Supervisor

  def start_link(init_arg) do
    Supervisor.start_link(__MODULE__, init_arg, name: __MODULE__)
  end

  @impl true
  def init(_init_arg) do
    children = [
      {Registry, keys: :unique, name: OrderBook.Registry},
      {DynamicSupervisor, name: OrderBook.DynamicSupervisor, strategy: :one_for_one}
    ]

    # If a child crashes, the supervisor restarts it with pristine state in < 1ms!
    Supervisor.init(children, strategy: :one_for_all)
  end
end

// actor/trading_actor.go
package main

import (
	"fmt"
	"log"
	"time"

	"github.com/asynkron/protoactor-go/actor"
)

// Message Definitions
type PlaceOrder struct {
	OrderID   string
	AmountUSD float64
}

type OrderProcessed struct {
	OrderID string
	Success bool
}

// 1. Actor Struct (State is 100% Private!)
type AccountActor struct {
	accountID string
	balance   float64
}

func (state *AccountActor) Receive(context actor.Context) {
	switch msg := context.Message().(type) {
	case *actor.Started:
		log.Printf("🚀 [ACTOR STARTED] AccountActor initialized for %s", state.accountID)

	case *PlaceOrder:
		// Process message sequentially with ZERO mutex locks!
		state.balance += msg.AmountUSD
		context.Respond(&OrderProcessed{OrderID: msg.OrderID, Success: true})

	case *actor.Stopping:
		log.Printf("🛑 Actor stopping...")
	}
}

func main() {
	system := actor.NewActorSystem()

	// 2. Spawn Actor Props
	props := actor.PropsFromProducer(func() actor.Actor {
		return &AccountActor{accountID: "acc_9842", balance: 1000.00}
	})

	pid, _ := system.Root.SpawnNamed(props, "account_acc_9842")

	// 3. Send 100,000 Concurrent Messages
	start := time.Now()
	for i := 0; i < 100000; i++ {
		system.Root.Send(pid, &PlaceOrder{OrderID: fmt.Sprintf("ord_%d", i), AmountUSD: 10.0})
	}

	log.Printf("⚡ Dispatched 100,000 actor messages in %v", time.Since(start))
}

       +-------------------------------------------------------------+
       |             Raw Message Processing Throughput (Msg/Sec)     |
       +-------------------------------------------------------------+
 Shared-Memory Mutex Locking (Go sync.Mutex)| ============= [3,200,000 msg/s]
 Elixir BEAM GenServer Process               | ================== [4,500,000 msg/s]
 ProtoActor Go (Lock-Free Mailbox)           | ==================================== [26,500,000 msg/s]
 Rust Tokio / Kameo Actor System             | ============================================= [52,000,000 msg/s]
                                             +-------------------------------------+
                                             0M     15M     30M     45M     60M

       +-------------------------------------------------------------+
       |             Memory Overhead for 1,000,000 Active Actors     |
       +-------------------------------------------------------------+
 OS Kernel Threads (pthread)                 | ==================================== [8,000 MB] (8 GB!)
 JVM Threads (Java Thread)                   | ============================ [4,000 MB]
 Elixir BEAM Lightweight Processes           | ============ [2,400 MB] (2.4 KB/Actor)
 Rust Kameo / Actix Async Actors             | == [480 MB] (Zero-Cost Concurrency!)
                                             +-------------------------------------+
                                             0MB    2000MB  4000MB  6000MB  8000MB