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
7 min read Core Entities JobDefinition: job_id, name, type (CRON, INTERVAL, ONE_TIME), schedule (cron expression or interval_seconds), handler (class name or function reference), Read article
6 min read The String Matching Problem Given a text T of length n and a pattern P of length m, find all Read article
6 min read Core Requirements 1:1 messaging and group chats. Real-time delivery (< 100ms latency). Message persistence: users can scroll back through history. Read article
7 min read Core Entities Property: property_id, address, city, state, zip, lat, lng, type (APARTMENT, HOUSE, CONDO, TOWNHOUSE), status (FOR_SALE, FOR_RENT, SOLD, OFF_MARKET), Read article
6 min read The Problem with Distributed Transactions In a monolith, a database transaction is atomic: either all changes commit or all roll Read article
6 min read Topological Sort A topological ordering of a directed acyclic graph (DAG) is a linear ordering of vertices such that for Read article
6 min read Core Entities Vehicle: vehicle_id, license_plate, type (SEDAN, VAN, TRUCK), capacity_kg, fuel_type, status (AVAILABLE, ON_TRIP, MAINTENANCE, OFFLINE), current_location (lat, lng), odometer_km, Read article
5 min read When Number Theory Appears in Interviews Number theory problems appear in interviews at companies like Google, Facebook, and competitive programming Read article
6 min read Core Entities Metric: metric_id, name, type (COUNTER, GAUGE, HISTOGRAM), unit, description, owner_id, created_at. DataPoint: metric_id, timestamp, value (DOUBLE), tags (key-value Read article
6 min read Core Entities Survey: survey_id, owner_id, title, description, status (DRAFT, ACTIVE, CLOSED), settings (allow_multiple_responses, anonymous, show_progress_bar), created_at, closes_at. Question: question_id, survey_id, Read article
6 min read Core Entities ContentType: type_id, name (Article, Page, Product), fields_schema (JSON schema defining the fields). Content: content_id, type_id, slug, status (DRAFT, Read article
