System Design

Requirements A typeahead service returns query suggestions as the user types. Google Search autocomplete, Twitter’s hashtag completion, and Stripe’s dashboard […]

Core Entities Hotel: hotel_id, name, address, star_rating, amenities (JSON array), check_in_time, check_out_time. RoomType: type_id, hotel_id, name (STANDARD, DELUXE, SUITE, PENTHOUSE),

Core Entities User: user_id, username (unique, URL-safe), email, password_hash, display_name, bio, avatar_url, role (READER, AUTHOR, EDITOR, ADMIN), created_at. Post: post_id,

Core Requirements A file sharing platform allows users to upload, organize, and share files and folders. Key features: file upload/download,

Core Entities Restaurant: restaurant_id, name, address, lat, lng, cuisine_type, rating, prep_time_minutes (avg), is_active, operating_hours. MenuItem: item_id, restaurant_id, name, description, price,

Requirements and Scope An appointment scheduling system allows users (customers) to book time slots with service providers (doctors, barbers, consultants).

Requirements A live comments system allows users to post comments on content (articles, videos, livestreams) and see other users’ comments

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

What is a Workflow Engine? A workflow engine executes multi-step processes where steps have dependencies, can run in parallel, and

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,

Core Responsibilities An identity service (also called an IAM or auth service) handles: Authentication (who are you?) — verifying credentials

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,

Core Architecture A search system takes a text query and returns a ranked list of documents (web pages, products, articles).

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,

What is a Document Store? A document store (MongoDB, DynamoDB, Couchbase, Firestore) stores JSON-like documents with flexible schemas — each