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System design patterns

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

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How to Implement CQRS with Separate Read and Write Models in Python

Implements Command Query Responsibility Segregation (CQRS) by splitting data into separate write and read models with dedicated repositories, using dataclasses for structure.

cqrs dataclasses repositories

Python

from dataclasses import dataclass, field
from typing import List, Dict, Optional


@dataclass
class OrderWriteModel:
    order_id: int
    customer: str
    items: List[str] = field(default_factory=list)

    def add_item(self, item: str) -> None:
        self.items.append(item)


@dataclass
class OrderReadModel:
    …

14 0 Open

System design patterns medium

How to Implement the Abstract Factory Pattern in Python

Implements the Abstract Factory pattern to create families of related GUI objects (buttons, checkboxes) without specifying their concrete classes.

abstract-factory design-patterns system-design

Python

from abc import ABC, abstractmethod


class Button(ABC):
    @abstractmethod
    def render(self):
        pass


class Checkbox(ABC):
    @abstractmethod
    def render(self):
        pass


class WindowsButton(Button):
    def render(self):
        return "Rendering Windows-style button"


class WindowsCheckbox(Chec…

13 0 Open

System design patterns medium

Inbox pattern consumer dedupe mock in Python

Implements a mock inbox consumer that deduplicates incoming messages by ID, with automatic eviction of old seen IDs to prevent unbounded memory growth.

deduplication inbox-pattern dataclasses

Python

import json
from collections import deque
from dataclasses import dataclass, field
from hashlib import sha256
from typing import Any


@dataclass
class InboxConsumer:
    max_seen: int = 1000
    seen_ids: set = field(default_factory=set)
    seen_history: deque = field(default_factory=deque)

    def _mark_seen(self,…

13 0 Open

System design patterns medium

Template Method Workflow Steps Base Class in Python

Define a reusable workflow skeleton in a base class and let subclasses fill in each step with the Template Method design pattern.

template-method design-patterns abc

Python

from abc import ABC, abstractmethod


class DataPipeline(ABC):
    """Template Method pattern: defines a workflow skeleton."""

    def run(self):
        """Template method - defines the algorithm's structure."""
        result = {"extracted": False, "transformed": False, "loaded": False}
        raw_data = self._ext…

13 0 Open

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