Reject Rate Alert: Monitor Service Reject Rate and Trigger Alerts on Threshold Breaches

Question

## Problem

A service logs each request as either `accepted` or `rejected`. Implement a `RejectRateMonitor` that tracks the reject rate over a sliding window of the last `W` seconds and fires an alert when the rate exceeds a threshold `T` for `C` consecutive evaluation intervals.

```python
class RejectRateMonitor:
    def __init__(self, window_sec: int, threshold: float, consecutive: int): ...

def record(self, timestamp: int, outcome: str) -> bool:
        """
        outcome: 'accepted' or 'rejected'
        Returns True if an alert should fire.
        """

def current_rate(self, timestamp: int) -> float: ...
```

**Example:**
```
m = RejectRateMonitor(window_sec=60, threshold=0.2, consecutive=3)
# Feed 100 events with 25% reject rate for 3 minutes...
m.record(180, "rejected")  -> True  # alert fires
```

## Follow-ups

1. How do you implement the sliding window efficiently — deque vs. circular buffer vs. bucketed counts?
2. What happens if events arrive out of order within the window? How do you handle late arrivals?
3. How do you reset the consecutive counter when the rate drops below the threshold?
4. If you have 10,000 services each with their own monitor, how do you centralize alerting without per-service polling?

Reject Rate Alert: Monitor Service Reject Rate and Trigger Alerts on Threshold Breaches

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