How to implement an idempotency key store in Python

import hashlib
import time
from typing import Dict, Optional


class IdempotencyStore:
    """Simple in-memory idempotency key store with mock processing."""

    def __init__(self, ttl_seconds: int = 3600) -> None:
        self.ttl = ttl_seconds
        self._store: Dict[str, tuple[str, float]] = {}

    def _is_expired(self, timestamp: float) -> bool:
        return (time.time() - timestamp) > self.ttl

    def get_or_process(self, key: str, data: str) -> tuple[bool, str]:
        """Return (processed, result). If key exists, return cached; else process."""
        if key in self._store and not self._is_expired(self._store[key][1]):
            return False, self._store[key][0]

        result = hashlib.sha256(f"{key}:{data}".encode()).hexdigest()[:16]
        self._store[key] = (result, time.time())
        return True, result


def main() -> None:
    store = IdempotencyStore(ttl_seconds=60)

    key = "order-123"
    payload = '{"product": "laptop"}'

    for call in range(3):
        was_processed, result = store.get_or_process(key, payload)
        status = "PROCESSED" if was_processed else "REUSED"
        print(f"Call {call + 1}: {status} | result={result}")


if __name__ == "__main__":
    main()