Database
An organized collection of data that can be easily accessed, managed, and updated. The backbone of almost every application.
What is Database?
An organized collection of data that can be easily accessed, managed, and updated. The backbone of almost every application.
Database is a foundational concept that sits in the Database Fundamentals area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Database" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Database in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Database lessonRelated lessons
Lessons that touch on Database as part of a larger topic.
Database Query Caching
Letting the database cache query results so the same question gets an instant answer
foundation · caching strategies
Database Functions
Reusable logic that lives inside the database, computed columns, transformations, and business rules
foundation · database fundamentals
Database Indexing
B-trees, hash indexes, composite indexes, covering indexes, the single biggest performance lever in any database
foundation · database fundamentals
Database Connection Pooling
PgBouncer, HikariCP, and why opening a new database connection per request is a recipe for disaster
foundation · database fundamentals
Time-Series Databases
Databases built for timestamped data, metrics, IoT sensors, financial ticks, and observability
intermediate · database types storage
See also
Related glossary terms you might want to look up next.
SQL
Structured Query Language for managing relational databases. Tables, rows, columns, and powerful joins to query related data.
NoSQL
Databases that don't use traditional table-based relational models. Includes document stores, key-value, graph, and column-family databases.
ACID
Four guarantees for database transactions: Atomicity (all or nothing), Consistency (valid states only), Isolation (no interference), Durability (changes persist).