Reference library

System design patterns

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

4 matches

Build a BFF (Backend for Frontend) Mock Aggregator in Python

A minimal HTTP server implementing the BFF pattern that aggregates user data and orders from two mock backends into a single JSON response.

bff http-server aggregation

Python

import json
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse


class MockBackendA:
    def get_user(self, user_id):
        return {"id": user_id, "name": "Alice", "service": "backend-a"}


class MockBackendB:
    def get_orders(self, user_id):
        return [
            {…

17 0 Open

System design patterns easy

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 easy

Idempotent Consumer: Store Processed IDs in Python

Implement an idempotent consumer that persists processed message IDs to a JSON file, skipping duplicates on restart.

idempotency duplicate-detection state-persistence

Python

import json
from pathlib import Path


class IdempotentStore:
    def __init__(self, storage_path: str = "processed_ids.json"):
        self.storage_path = Path(storage_path)
        self.processed_ids = self._load()

    def _load(self) -> set:
        if self.storage_path.exists():
            with self.storage_path…

15 0 Open

System design patterns medium

Singleton Config Loader in Python with Caution

Implements a singleton config loader in Python that reads JSON config files, but demonstrates the hidden gotcha of shared state across instances.

singleton config design-patterns

Python

import json
from pathlib import Path

class ConfigLoader:
    _instance = None

    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self, config_file="config.json"):
        if not hasattr(self, "loaded…

11 0 Open

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