Microservices Architecture Guide 2026: Design, Communication and Resilience

E-commerce domain bounded contexts:

Order Service (owns orders, order items)
  - Create order
  - Update order status
  - Get order history

Product Service (owns products, inventory)
  - List products
  - Update inventory
  - Product search

User Service (owns users, auth)
  - Register, login
  - Profile management
  - Authentication tokens

Payment Service (owns payment processing)
  - Process payment
  - Handle refunds
  - Payment status

Notification Service (owns notifications)
  - Email, SMS, push
  - Triggered by events from other services

Each service:
  - Has its own database (database-per-service pattern)
  - Is owned by one team
  - Can be deployed independently
  - Communicates via API or events (not shared DB)

# REST API call between services
import httpx
from tenacity import retry, stop_after_attempt, wait_exponential

@retry(stop=stop_after_attempt(3), wait=wait_exponential(multiplier=1, min=1, max=10))
async def get_user(user_id: int) -> dict:
    async with httpx.AsyncClient(base_url="http://user-service:8001") as client:
        r = await client.get(f"/api/users/{user_id}", timeout=5.0)
        r.raise_for_status()
        return r.json()

# Use circuit breaker for resilience
from circuitbreaker import circuit

@circuit(failure_threshold=5, recovery_timeout=30)
async def call_payment_service(order_id: int, amount: float):
    async with httpx.AsyncClient(timeout=10) as client:
        return await client.post("http://payment-service/payments",
                                 json={"order_id": order_id, "amount": amount})

from aiokafka import AIOKafkaProducer, AIOKafkaConsumer
import json

# Produce event when order is created
async def publish_order_created(order: dict):
    producer = AIOKafkaProducer(bootstrap_servers="kafka:9092")
    await producer.start()
    try:
        event = {
            "event_type": "order.created",
            "order_id": order["id"],
            "user_id": order["user_id"],
            "total": order["total"],
            "timestamp": datetime.utcnow().isoformat()
        }
        await producer.send("orders", json.dumps(event).encode())
    finally:
        await producer.stop()

# Notification service consumes the event
async def consume_order_events():
    consumer = AIOKafkaConsumer(
        "orders",
        bootstrap_servers="kafka:9092",
        group_id="notification-service",
        auto_offset_reset="earliest"
    )
    await consumer.start()
    async for msg in consumer:
        event = json.loads(msg.value)
        if event["event_type"] == "order.created":
            await send_confirmation_email(event["user_id"], event["order_id"])

# Kong / nginx / custom gateway routes
# All clients talk to one entry point:
# POST /api/orders -> Order Service :8001
# GET /api/products -> Product Service :8002
# POST /api/auth -> User Service :8003

# Kong route configuration
routes:
  - name: orders
    paths: ["/api/orders"]
    service: order-service
    plugins:
      - name: jwt           # validate JWT
      - name: rate-limiting # 100/min per user
      - name: request-transformer

  - name: products
    paths: ["/api/products"]
    service: product-service
    plugins:
      - name: response-ratelimiting

# OpenTelemetry — trace requests across services
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.exporter.jaeger.thrift import JaegerExporter
from opentelemetry.sdk.trace.export import BatchSpanProcessor

# Setup (once at startup)
provider = TracerProvider()
jaeger_exporter = JaegerExporter(agent_host_name="jaeger", agent_port=6831)
provider.add_span_processor(BatchSpanProcessor(jaeger_exporter))
trace.set_tracer_provider(provider)
tracer = trace.get_tracer(__name__)

# Instrument FastAPI
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
from opentelemetry.instrumentation.httpx import HTTPXClientInstrumentor

FastAPIInstrumentor.instrument_app(app)  # auto-instruments all routes
HTTPXClientInstrumentor().instrument()   # auto-instruments httpx calls

# Manual span for business logic
async def process_order(order_id: int):
    with tracer.start_as_current_span("process_order") as span:
        span.set_attribute("order.id", order_id)
        order = await get_order(order_id)
        span.set_attribute("order.total", order["total"])
        await charge_payment(order)
        await send_confirmation(order)

from fastapi import FastAPI
from datetime import datetime

app = FastAPI()

@app.get("/health")
async def health():
    return {
        "status": "healthy",
        "timestamp": datetime.utcnow().isoformat(),
        "version": "1.2.3",
        "dependencies": {
            "database": await check_db(),
            "redis": await check_redis(),
        }
    }

@app.get("/ready")
async def readiness():
    # Check if service can handle traffic
    if not db_pool or not redis_client:
        raise HTTPException(503, "Service not ready")
    return {"status": "ready"}

# Kubernetes probes:
# livenessProbe: /health (if fails: restart container)
# readinessProbe: /ready (if fails: remove from load balancer)