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System design patterns

Sharding, load balancing, CAP tradeoffs, and scaling patterns — interview and production ready.

4 matches

How to Implement the Repository Pattern in Python with an In-Memory Dict

Stores, retrieves, updates, and deletes user records in memory using a Repository abstraction over a plain dict, isolating data access from business logic.

repository-pattern design-patterns in-memory

Python

class UserRepository:
    def __init__(self):
        self._storage = {}
        self._next_id = 1

    def create(self, name, email):
        user_id = self._next_id
        self._next_id += 1
        self._storage[user_id] = {"id": user_id, "name": name, "email": email}
        return self._storage[user_id]

    def…

11 0 Open

System design patterns easy

How to Mock Hexagonal Architecture Ports and Adapters in Python

Mock an email adapter in a hexagonal architecture with unittest.mock to test business logic in isolation.

hexagonal-architecture unittest-mock dependency-injection

Python

from unittest.mock import Mock

class EmailService:
    def send(self, recipient, message):
        raise NotImplementedError

class OrderProcessor:
    def __init__(self, email_service):
        self.email_service = email_service
    
    def process_order(self, order_id, customer_email):
        # Business logic
   …

15 0 Open

System design patterns easy

How to mock the domain center in an onion architecture in Python

Define a repository interface and an in-memory mock to test domain services without touching infrastructure.

onion-architecture repository-pattern dependency-injection

Python

from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import Dict, List, Optional


@dataclass
class Order:
    id: int
    customer: str
    items: List[str]
    total: float


class OrderRepository(ABC):
    @abstractmethod
    def find_by_id(self, order_id: int) -> Optional[Order]:
     …

11 0 Open

System design patterns easy

Python MVC Pattern Example (Model-View-Controller)

A minimal, runnable Model-View-Controller (MVC) example in pure Python that separates data, presentation, and logic.

mvc design-pattern architecture

Python

class Model:
    def __init__(self):
        self.data = {"title": "Initial Title", "content": "Initial Content"}

    def get_data(self):
        return self.data

    def update_data(self, title=None, content=None):
        if title:
            self.data["title"] = title
        if content:
            self.data["c…

15 0 Open

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