Software Development Engineer, PubTech, Supply Tech - Forecasting Services

Amazon

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself). For example: If the tree is [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1, then the expected output is 3, because the LCA of nodes 5 and 1 is 3. If the tree is [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4, then the expected output is 5, because the LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition. If the tree is [1,2], p = 1, q = 2, then the expected output is 1. Consider these constraints: The number of nodes in the tree is in the range [2, 10^5]. -10^9 <= Node.val <= 10^9 All Node.val are unique. p != q p and q will exist in the tree.

Amazon

Let's design a Twitter-like service. Consider the following: Core Functionality: How would you implement the ability for users to post tweets, follow other users, and view a timeline of tweets from the users they follow? Data Model: What database schema would you use to store tweets, user information, and follower relationships? Consider scalability and efficiency for reads and writes. Scalability: How would you handle a large number of users and tweets? Discuss strategies for sharding, caching, and load balancing. Real-time Updates: How would you ensure that users see new tweets in their timeline in near real-time? Consider using technologies like WebSockets or Server-Sent Events. Search: How would you implement a search feature that allows users to find tweets containing specific keywords or hashtags? Think about indexing strategies and search algorithms. Rate Limiting: How would you prevent abuse and ensure fair usage of the service? Describe your approach to rate limiting API requests. Example Scenario: Imagine a user, Alice, follows 1,000 other users, including Bob. Bob posts a tweet. Explain how that tweet would propagate to Alice's timeline, considering potential performance bottlenecks. Technology Stack: What technologies (programming languages, frameworks, databases, etc.) would you choose and why?

Amazon

Tell me about a time you exemplified one of Amazon's leadership principles. For example, consider the 'Customer Obsession' principle. Can you describe a situation where you went above and beyond to meet a customer's needs, even when it was challenging or required you to think outside the box? What specific actions did you take, and what was the outcome? Alternatively, let's explore the 'Bias for Action' principle. Share an instance where you had to make a quick decision with limited information. What was the situation, what factors did you consider, and how did you mitigate the risks associated with acting swiftly? Or perhaps you can elaborate on a time you demonstrated 'Ownership.' Describe a project or task where you took full responsibility for the outcome, even when things didn't go as planned. How did you handle the setbacks, and what did you learn from the experience? Another good principle to discuss could be 'Invent and Simplify.' Tell me about a time you created an innovative solution to a complex problem, while keeping it simple and easy to use. What was the problem, what was your solution, and how did you ensure its simplicity? Finally, tell me about a time where you had to 'Learn and Be Curious'.