Software Engineer · Phone Screen · Coding

Netflix — Software Engineer ✅ Passed

Level: Mid-Level

Round: Phone Screen · Type: Coding · Difficulty: 7/10 · Duration: 60 min · Interviewer: Unfriendly

Topics: Concurrency, Data Structures, Algorithms

Location: Los Gatos, CA

Interview date: 2025-12-31

Summary

I was asked to design a Latency Tracker class.

The class needs to provide two functionalities:

1. Store latency samples, with inputs being timestamp and latency in milliseconds.
2. Query the specified percentile latency within a given window, with inputs being time window and percentile.

The class needs to support concurrency.

Details

The coding question I got was to implement a Latency Tracker class with the following functionalities:

` class LatencyTracker: def init(self): # Implementation details pass

def store_latency(self, timestamp, latency_ms):
    # Stores latency sample with timestamp
    pass

def get_percentile_latency(self, time_window, percentile):
    # Returns the specified percentile latency within the given time window
    pass

`

My approach:

1. I analyzed the requirements for concurrency support, considering thread safety.
2. I chose appropriate data structures to store the latency samples efficiently.
3. I implemented the store_latency method to handle concurrent writes.
4. I implemented the get_percentile_latency method, ensuring it can handle concurrent reads and writes.

Key insights:

• Consider thread safety when designing for concurrency.
• Choosing appropriate data structures is crucial for efficiency.
• Handle concurrent reads and writes carefully to avoid race conditions.