6 min read Choosing the Right Algorithm Unweighted graph (or all weights equal): BFS gives the shortest path in O(V+E). Weighted graph, non-negative […] Read article
7 min read Core Entities Restaurant: restaurant_id, name, address, lat, lng, cuisine_type, rating, is_open, prep_time_minutes (average). MenuItem: item_id, restaurant_id, name, description, price, category, Read article
7 min read Overview An ad server matches advertisers’ ads to available ad slots on publisher pages in real time. The two main Read article
6 min read Core Entities Hotel: hotel_id, name, address, city, star_rating, amenities (JSON), check_in_time, check_out_time. RoomType: room_type_id, hotel_id, name (STANDARD, DELUXE, SUITE), max_occupancy, Read article
6 min read What is Event Sourcing? In traditional systems, the database stores the current state: the orders table has one row per Read article
5 min read Core Interval Pattern Interval problems involve ranges [start, end] and typically ask: merge overlapping intervals, find gaps, count the minimum Read article
6 min read What is Multi-Tenancy A multi-tenant SaaS serves multiple customers (tenants) from the same shared infrastructure. Each tenant’s data must be Read article
6 min read Problem and Naive DP LIS: find the length of the longest strictly increasing subsequence of an array. Elements of the Read article
7 min read Core Entities Plan: plan_id, name, billing_cycle (MONTHLY, ANNUAL, WEEKLY), price_cents, currency, trial_days, features (JSON). Subscription: subscription_id, customer_id, plan_id, status (TRIALING, Read article
7 min read Problem Scope Given a prefix typed by the user, return the top-K (typically 5-10) suggestions ranked by relevance. Used in Read article
6 min read Tree DP Pattern Many tree problems require computing an answer that depends on both subtrees. The key pattern: define a Read article
7 min read Core Entities Flight: flight_id, airline, flight_number, origin_airport, destination_airport, departure_time, arrival_time, aircraft_type, status (SCHEDULED, BOARDING, DEPARTED, ARRIVED, CANCELLED, DELAYED). Seat: seat_id, Read article
6 min read The Three Pillars of Observability Observability lets engineers understand the internal state of a system from its external outputs. Three Read article
6 min read What Makes an Algorithm Greedy A greedy algorithm makes the locally optimal choice at each step, hoping this leads to Read article
6 min read Palindrome Check A palindrome reads the same forward and backward. Brute force check: O(n). Two-pointer: left=0, right=n-1; while left < Read article
