Research Engineer, Machine Learning L6

Netflix

Design and implement an LRU (Least Recently Used) cache. Your cache should support the following operations: get(key) - Gets the value (will always be positive) of the key if the key exists in the cache, otherwise returns -1. put(key, value) - Sets or inserts the value if the key is not already present. When the cache reaches its capacity, it should invalidate the least recently used item before inserting a new item. For the purpose of this question, when a new key is inserted, regard it as most recently used. The cache is initialized with a positive capacity. Example: LRUCache cache = new LRUCache(2); // capacity is 2 cache.put(1, 1); cache.put(2, 2); cache.get(1); // returns 1 cache.put(3, 3); // evicts key 2 cache.get(2); // returns -1 (not found) cache.put(4, 4); // evicts key 1 cache.get(1); // returns -1 (not found) cache.get(3); // returns 3 cache.get(4); // returns 4 Follow up: Could you do both operations in O(1) time complexity?

Netflix

Let's say Netflix is experiencing slow streaming speeds for users in a specific geographic region. As a software engineer, how would you approach diagnosing and resolving this issue? Be specific and consider the following: Initial Assessment: What steps would you take to confirm the issue and gather initial data? Consider the metrics you'd want to examine, such as: Average buffering times Error rates during playback Network latency CPU/Memory utilization on streaming servers Possible Causes: Outline potential causes for the slow streaming speeds. Think about factors like: Network congestion in the region Issues with Netflix's content delivery network (CDN) servers in that region Problems with peering agreements with local ISPs Software bugs in the Netflix app or streaming infrastructure Unexpected spikes in user traffic Troubleshooting Steps: Describe the troubleshooting steps you would take to narrow down the cause. This could involve: Analyzing server logs for errors Running network diagnostics (e.g., traceroute, ping) to identify bottlenecks Testing different CDN servers in the region Checking the health of the origin servers Simulating user traffic to stress-test the system Resolution: How would you address the identified cause? This might include: Re-routing traffic to different CDN servers Increasing server capacity in the affected region Optimizing the streaming protocol or encoding settings Working with ISPs to improve network connectivity Deploying software fixes to address bugs Prevention: What measures can be taken to prevent similar issues from occurring in the future? Consider: Improving monitoring and alerting systems Implementing automated failover mechanisms Regularly stress-testing the infrastructure Diversifying CDN providers For example, if high network latency is detected, how would you investigate the path between Netflix's servers and the user's devices? What tools would you use, and what specific data points would you look for? Explain your reasoning behind each step and how it contributes to solving the problem. Detail the specific technologies and Netflix-specific knowledge you would need to effectively troubleshoot.

Netflix

Tell me about a time you had to make a difficult decision with incomplete information. What was the situation? What information was missing? What decision did you make and how did you arrive at it? What was the outcome? What did you learn from the experience? For example, perhaps you had to decide whether to launch a new feature without complete user testing data, or whether to pursue a new market opportunity without a full understanding of the competitive landscape. Maybe you had to make a critical hiring decision without all the information you needed about the candidate's past performance. The key is to show that you can assess risks, weigh potential outcomes, and make sound judgments even when things are uncertain. Be sure to articulate the reasoning that led you to your decision, and reflect on the lessons you learned from the experience. This demonstrates your adaptability, problem-solving abilities, and your capacity for learning and growth.