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System design patterns

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

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Create a Data Helper Class in Python

A reusable DataHelper class that saves and loads JSON and CSV files from a configurable base directory, with automatic header detection for CSV.

data-helper json csv

Python

import json
import csv
from pathlib import Path

class DataHelper:
    def __init__(self, base_path="."):
        self.base_path = Path(base_path)
        self.base_path.mkdir(exist_ok=True)

    def save_json(self, data, filename):
        path = self.base_path / filename
        with open(path, "w") as f:
          …

15 0 Open

System design patterns medium

How to Implement a Simple MVVM Binding Mock in Python

A minimal Python implementation of the MVVM pattern, mocking data binding so views auto-update when the view model changes.

mvvm binding observer pattern

Python

class BindingMock:
    def __init__(self, view_model):
        self.view_model = view_model
        self.subscribers = []

    def bind(self, property_name, callback):
        self.subscribers.append((property_name, callback))

    def set(self, property_name, value):
        setattr(self.view_model, property_name, va…

18 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

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