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System design patterns

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

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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…
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