Software Engineering, Platform Modernization Engineering - L5

Netflix

You are given the definition of a binary tree node: class Node: def init(self, val=0, left=None, right=None): self.val = val self.left = left self.right = right Write a function is_bst(root) that takes the root of a binary tree as input and returns True if the tree is a valid Binary Search Tree (BST), and False otherwise. Definition of a BST: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with keys greater than the node's key. Both the left and right subtrees must also be binary search trees. Example 1: Input: root = [2,1,3] Output: true 2 / 1 3 Example 2: Input: root = [5,1,4,null,null,3,6] Output: false 5 / 1 4 / 3 6 Explanation: The root node's value is 5 but its right child's value is 4. Constraints: The number of nodes in the tree is in the range [1, 10000]. -10000 <= Node.val <= 10000 Your solution should handle edge cases such as an empty tree or a tree with only one node.

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

Could you elaborate on some challenges you've encountered while working with Java and Scala?