Core Entities Company: company_id, name, description, logo_url, website, size, industry, verified (boolean). Job: job_id, company_id, title, description, location, is_remote, employment_type […]
Two-Pointer Core Idea Two pointers maintain two indices into a sorted or structured array, moving toward each other or in
Requirements A live comments system allows users to post comments on content (articles, videos, livestreams) and see other users’ comments
Core Entities Contact: contact_id, first_name, last_name, email (unique), phone, company_id, job_title, source (INBOUND, OUTBOUND, REFERRAL), owner_id (assigned sales rep), created_at,
What is a Workflow Engine? A workflow engine executes multi-step processes where steps have dependencies, can run in parallel, and
Core Entities PaymentIntent: intent_id (UUID), merchant_id, customer_id, amount (integer cents), currency, status (CREATED, PROCESSING, REQUIRES_ACTION, SUCCEEDED, FAILED, CANCELLED, REFUNDED), payment_method_id,
Union-Find Core Concept Union-Find (Disjoint Set Union, DSU) efficiently tracks which elements belong to the same connected component. Two operations:
Core Responsibilities An identity service (also called an IAM or auth service) handles: Authentication (who are you?) — verifying credentials
Core Entities User: user_id, email, timezone, working_hours (JSON: {mon: “9:00-17:00”, …}). Calendar: calendar_id, user_id, name, color, is_primary, visibility (PRIVATE, PUBLIC,
Sliding Window Core Idea Sliding window maintains a window [left, right] over a linear data structure (array, string). As the
Core Architecture A search system takes a text query and returns a ranked list of documents (web pages, products, articles).
Core Requirements A collaborative document editor allows multiple users to edit the same document simultaneously, with changes reflected in near-real-time
When Does Greedy Work? Greedy works when the locally optimal choice at each step leads to a globally optimal solution.
What is a Document Store? A document store (MongoDB, DynamoDB, Couchbase, Firestore) stores JSON-like documents with flexible schemas — each
Core Entities Event: event_id, name, venue_id, event_date, doors_open, start_time, status (ON_SALE, SOLD_OUT, CANCELLED, COMPLETED), total_capacity. Venue: venue_id, name, address, seating_map_url,
