/microservices-patterns

name: microservices-patterns
description: Design microservices architectures with service boundaries, event-driven communication, and resilience patterns. Use when building distributed systems, decomposing monoliths, or implementing microservices.
license: MIT

Microservices Patterns

Master microservices architecture patterns including service boundaries, inter-service communication, data management, and resilience patterns for building distributed systems.

When to Use This Skill

• Decomposing monoliths into microservices
• Designing service boundaries and contracts
• Implementing inter-service communication
• Managing distributed data and transactions
• Building resilient distributed systems
• Implementing service discovery and load balancing
• Designing event-driven architectures

Core Concepts

1. Service Decomposition Strategies

**By Business Capability**

• Organize services around business functions
• Each service owns its domain
• Example: OrderService, PaymentService, InventoryService

**By Subdomain (DDD)**

• Core domain, supporting subdomains
• Bounded contexts map to services
• Clear ownership and responsibility

**Strangler Fig Pattern**

• Gradually extract from monolith
• New functionality as microservices
• Proxy routes to old/new systems

2. Communication Patterns

**Synchronous (Request/Response)**

• REST APIs
• gRPC
• GraphQL

**Asynchronous (Events/Messages)**

• Event streaming (Kafka)
• Message queues (RabbitMQ, SQS)
• Pub/Sub patterns

3. Data Management

**Database Per Service**

• Each service owns its data
• No shared databases
• Loose coupling

**Saga Pattern**

• Distributed transactions
• Compensating actions
• Eventual consistency

4. Resilience Patterns

**Circuit Breaker**

• Fail fast on repeated errors
• Prevent cascade failures

**Retry with Backoff**

• Transient fault handling
• Exponential backoff

**Bulkhead**

• Isolate resources
• Limit impact of failures

Service Decomposition Patterns

Pattern 1: By Business Capability

# Order Service
class OrderService:
    async def create_order(self, order_data: dict) -> Order:
        order = Order.create(order_data)
        await self.event_bus.publish(
            OrderCreatedEvent(order_id=order.id, customer_id=order.customer_id)
        )
        return order

# Payment Service (separate service)
class PaymentService:
    async def process_payment(self, payment_request: PaymentRequest) -> PaymentResult:
        result = await self.payment_gateway.charge(
            amount=payment_request.amount,
            customer=payment_request.customer_id
        )
        if result.success:
            await self.event_bus.publish(
                PaymentCompletedEvent(order_id=payment_request.order_id)
            )
        return result

# Inventory Service (separate service)
class InventoryService:
    async def reserve_items(self, order_id: str, items: List[OrderItem]) -> ReservationResult:
        for item in items:
            available = await self.inventory_repo.get_available(item.product_id)
            if available < item.quantity:
                return ReservationResult(success=False, error=f"Insufficient inventory")

        reservation = await self.create_reservation(order_id, items)
        await self.event_bus.publish(InventoryReservedEvent(order_id=order_id))
        return ReservationResult(success=True, reservation=reservation)

Pattern 2: API Gateway

from fastapi import FastAPI
import httpx

class APIGateway:
    """Central entry point for all client requests."""

    def __init__(self):
        self.order_service_url = "http://order-service:8000"
        self.payment_service_url = "http://payment-service:8001"
        self.http_client = httpx.AsyncClient(timeout=5.0)

    @circuit(failure_threshold=5, recovery_timeout=30)
    async def call_order_service(self, path: str, method: str = "GET", **kwargs):
        """Call order service with circuit breaker."""
        response = await self.http_client.request(
            method, f"{self.order_service_url}{path}", **kwargs
        )
        response.raise_for_status()
        return response.json()

    async def create_order_aggregate(self, order_id: str) -> dict:
        """Aggregate data from multiple services."""
        order, payment, inventory = await asyncio.gather(
            self.call_order_service(f"/orders/{order_id}"),
            self.call_payment_service(f"/payments/order/{order_id}"),
            self.call_inventory_service(f"/reservations/order/{order_id}"),
            return_exceptions=True
        )

        result = {"order": order}
        if not isinstance(payment, Exception):
            result["payment"] = payment
        if not isinstance(inventory, Exception):
            result["inventory"] = inventory
        return result

Communication Patterns

Pattern 1: Synchronous REST Communication

import httpx
from tenacity import retry, stop_after_attempt, wait_exponential

class ServiceClient:
    """HTTP client with retries and timeout."""

    def __init__(self, base_url: str):
        self.base_url = base_url
        self.client = httpx.AsyncClient(timeout=httpx.Timeout(5.0, connect=2.0))

    @retry(stop=stop_after_attempt(3), wait=wait_exponential(multiplier=1, min=2, max=10))
    async def get(self, path: str, **kwargs):
        """GET with automatic retries."""
        response = await self.client.get(f"{self.base_url}{path}", **kwargs)
        response.raise_for_status()
        return response.json()

payment_client = ServiceClient("http://payment-service:8001")
result = await payment_client.get("/payments/123")

Pattern 2: Asynchronous Event-Driven

from aiokafka import AIOKafkaProducer, AIOKafkaConsumer
import json

class EventBus:
    """Event publishing and subscription."""

    async def publish(self, event: DomainEvent):
        """Publish event to Kafka topic."""
        await self.producer.send_and_wait(