Database

A database is an organized collection of structured or semi-structured data stored electronically, usually managed by a database management system (DBMS). Applications talk to it through a query language or API to store, find, change, and delete records.

Why it matters

Almost every website, app, and online service keeps its state in a database: user accounts, orders, posts, settings. Unlike a plain file, a database gives you fast lookups, controlled concurrent access by many users, constraints that keep data valid, and recovery after a crash. When the database is slow or unreachable, the application on top of it usually fails too, which is why database health is a core part of uptime monitoring.

Example

A small shop might keep three kinds of data in one database:

customers  (id, name, email)
products   (id, title, price)
orders     (id, customer_id, product_id, created_at)

A single query can answer "which customers ordered product 42 this week?" without scanning every record by hand.

Common mistakes

• Treating a database as a spreadsheet. Concurrency, constraints, and indexes behave very differently from a shared file.
• Running the database on the same server as the web app with no backups, so one disk failure loses everything.
• Assuming "database" means "SQL". Many databases, such as document and key-value stores, do not use SQL.

Related

• DBMS
• Relational database
• NoSQL
• Database backup

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