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System design patterns

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

3 matches

Facade Pattern in Python with Mock Simplification

This code demonstrates the Facade pattern by hiding complex subsystem interactions behind a simple start/stop interface, and adds a MockFacade for testing failure scenarios.

facade-pattern design-patterns abstraction

Python

class SubsystemA:
    def operation_a(self):
        return "Subsystem A: ready"

class SubsystemB:
    def operation_b(self):
        return "Subsystem B: ready"

class SubsystemC:
    def operation_c(self):
        return "Subsystem C: ready"


class Facade:
    def __init__(self):
        self._a = SubsystemA()
   …

15 0 Open

System design patterns easy

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 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

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