Visualizing the Product Inventory System

#GoogleWSE#Series#Intermediate

Visualizing the Product Inventory System --- Google WSE Interview Series: 1. Part 1: Map & Heap Deep Dive 2. Part 2: The Reality Check Explained 3. Part 3: Adva

Visualizing the Product Inventory System --- Google WSE Interview Series: 1. Part 1: Map & Heap Deep Dive 2. Part 2: The Reality Check Explained 3. Part 3: Advanced Follow-up Solutions 4. Visual Explanation: Process Flow --- To understand how the system manages millions of orders with sub-millisecond latency, let's look at the interaction between the Min-Heap and the Valid Orders Map. The Core Concept: "Truth vs. Cache" - Valid Orders Map (The Truth): This is our source of truth. If a timestamp isn't in this map, the order doesn't exist. - Min-Heap (The Cache): This is a fast-access "suggestion" of what the minimum might be. It might contain "ghost" orders (stale prices or deleted orders) to avoid expensive $O(N)$ heap removals. --- 1. Submitting Orders When you call submitOrder(price, timestamp), we do two things: 1. Update The Truth (Map). 2. Add a new entry to The Cache (Heap). --- 2. Lazy Deletion in Action When you call removeOrder(10), we only remove it from the Map. We leave the $100 in the heap. This is why it's "Lazy". --- 3. Retreiving Min Price (The Cleanup) When you call getMinPrice(), the system looks at the top of the heap. It then performs a "Reality Check" against the map. --- Why this is "Google Scale" 1. Writing is fast: Adding to a map and heap is $O(\log N)$. 2. Deleting is Instant: Deleting from a map is $O(1)$. We don't waste time re-balancing the heap during deletion. 3. Reading is Efficient: We only pay the price of "cleaning" the heap when we actually need the result. If a deleted item is buried deep in the heap, it never bothers us! --- Explore the code: Part 2: The Reality Check Explained