**Design a Data Warehouse Schema**\nYou are tasked with designing a data warehouse schema for an online retail company that needs to analyze customer behavior. The company wants to track user purchases, product categories, and sales over time. Describe the overall architecture, including the choice of databases, ETL processes, and data models you would use to achieve this. Discuss how data consistency and scalability can be maintained.\n

**LeetCode #15 - 3Sum**\nGiven an array of integers, find all the unique triplets (a, b, c) such that a + b + c = 0, where a, b, and c are distinct indices in the array. You must return the result in a specific order of triplets.\n\n**Example 1:**\nInput: `[-1, 0, 1, 2, -1, -4]`\nOutput: `[[-1, -1, 2], [-1, 0, 1]]`\nExplanation: `-1 + -1 + 2 = 0` and `-1 + 0 + 1 = 0` are the two unique triplets.\n\n**Example 2:**\nInput: `[0, 1, 1]`\nOutput: `[]`\nExplanation: No triplet exists that sums to zero.\n\n**Constraints:**\n- 0 <= nums.length <= 3000\n- -10^5 <= nums[i] <= 10^5\n

Explain how garbage collection works in Java. What are the different types of garbage collectors available in the Java Virtual Machine (JVM), and how would you choose one based on the use case?\n