System Design

⏱ 6 min read Core Entities Property: (property_id, listing_type=SALE|RENT, status=ACTIVE|PENDING|SOLD|WITHDRAWN, address, geo_point, price_cents, bedrooms, bathrooms, sqft, year_built, property_type=HOUSE|CONDO|APARTMENT|LAND, description, agent_id, created_at). PropertyImage: (image_id, property_id, […] Read article

⏱ 6 min read The Feed Problem A social network feed shows a user the recent posts from people they follow, ranked by relevance Read article

⏱ 6 min read Core Entities Coupon: (coupon_id, code, discount_type=PERCENTAGE|FIXED_AMOUNT|FREE_SHIPPING|BUY_X_GET_Y, discount_value, min_order_amount_cents, max_discount_cents, start_date, end_date, is_active, usage_limit_global, usage_limit_per_user, applicable_to=ALL|CATEGORY|PRODUCT, applicable_ids[]). CouponUsage: (usage_id, coupon_id, user_id, Read article

⏱ 6 min read Core Entities Board: (board_id, workspace_id, name, visibility=PUBLIC|PRIVATE, owner_id, created_at). A board represents a project. Column: (column_id, board_id, name, position, wip_limit). Read article

⏱ 6 min read Why Sharding? A single database server has limits: storage capacity (~tens of terabytes), write throughput (~tens of thousands of writes/second), Read article

⏱ 4 min read Core Entities Wallet: (wallet_id, user_id, currency, balance_cents, status=ACTIVE|FROZEN|CLOSED, created_at). One user may have multiple wallets (different currencies). LedgerEntry: (entry_id, wallet_id, Read article

⏱ 6 min read The Consensus Problem In a distributed system, multiple nodes must agree on a single value (which node is the leader, Read article

⏱ 6 min read Core Entities LeaveType: (leave_type_id, name, accrual_rate_days_per_month, max_balance_days, carry_over_max_days, is_paid, requires_documentation). Examples: Annual Leave (1.67 days/month, max 30 days), Sick Leave Read article

⏱ 6 min read The Three Pillars of Observability Observability is the ability to understand the internal state of a system from its external Read article

⏱ 6 min read Core Entities Ticket: ticket_id, customer_id, subject, description, priority (LOW, MEDIUM, HIGH, URGENT), status (OPEN, IN_PROGRESS, WAITING_ON_CUSTOMER, RESOLVED, CLOSED), category, assigned_agent_id, Read article

⏱ 5 min read Core Entities PaymentIntent: intent_id (idempotency key), amount_cents, currency, customer_id, payment_method_id, status (CREATED, PROCESSING, SUCCEEDED, FAILED, CANCELLED), created_at, metadata. PaymentMethod: method_id, Read article

⏱ 6 min read Core Entities Post: post_id, user_id, content, media_urls[], platforms[] (TWITTER, INSTAGRAM, LINKEDIN, FACEBOOK), scheduled_at (UTC), status (DRAFT, SCHEDULED, PUBLISHING, PUBLISHED, FAILED), Read article

⏱ 6 min read Why Distributed Locks? A mutex works within a single process. A database row lock works within a single database. When Read article

⏱ 6 min read Core Entities Order: order_id, customer_id, restaurant_id, driver_id, items[], total_cents, status, placed_at, estimated_delivery_at. OrderStatus (state machine): PLACED -> CONFIRMED -> PREPARING Read article

⏱ 6 min read The Problem with Distributed Transactions In a monolith with a single database, ACID transactions guarantee atomicity: either all operations succeed Read article