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System design patterns

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

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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…
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