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System design patterns

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

3 matches

Builder pattern for mocking complex objects in Python

Use a fluent Builder to construct realistic mock objects with defaults, enabling readable test data setup.

class User:
    def __init__(self):
        self.name = "default"
        self.age = 0
        self.email = "unknown@example.com"
        self.address = "unknown"

    def __repr__(self):
        return f"User(name={self.name!r}, age={self.age}, email={self.email!r}, address={self.address!r})"


class UserBuilder:
   …

16 0 Open

System design patterns easy

How to Aggregate Mock API Routes by Method in Python

Groups mock API routes by path and method, collecting response bodies and counts into a nested dictionary structure.

defaultdict api-gateway aggregation

Python

from collections import defaultdict


def aggregate_mock_routes(routes):
    """Aggregate mock API routes by method and aggregate their response bodies."""
    aggregated = defaultdict(lambda: defaultdict(list))

    for route in routes:
        method = route["method"]
        path = route["path"]
        response = …

13 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]:
     …

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