import time
import heapq
from typing import Optional

class TTLCache:
    def __init__(self):
        self.cache: dict[str, tuple[any, float]] = {}  # key -> (value, expiry)
        self.expiry_heap: list[tuple[float, str]] = []  # min-heap: (expiry, key)

    def set(self, key: str, value: any, ttl_seconds: float) -> None:
        expiry = time.time() + ttl_seconds
        self.cache[key] = (value, expiry)
        heapq.heappush(self.expiry_heap, (expiry, key))

    def get(self, key: str) -> Optional[any]:
        self._cleanup()
        if key not in self.cache:
            return None
        value, expiry = self.cache[key]
        if time.time() > expiry:
            del self.cache[key]
            return None
        return value

    def _cleanup(self) -> None:
        now = time.time()
        while self.expiry_heap and self.expiry_heap[0][0] < now:
            expiry, key = heapq.heappop(self.expiry_heap)
            if key in self.cache and self.cache[key][1] <= now:
                del self.cache[key]

System Design for Coding Interviews — mini designs

System Design for Coding Interviews — mini designs

System Design for Coding Interviews — mini designs