Database Glossary

Browse 78 database terms defined in plain English, from the cultural dictionary of computing.

78 Database Terms

B+ Tree
A self-balancing tree variant where all data resides in leaf nodes (linked for efficient range scans), and internal nodes only store keys for routing. The...
Change Data Capture
A pattern for tracking and streaming row-level changes (inserts, updates, deletes) from a database to downstream systems in real-time. Tools like Debezium read...
Connection Leak
A bug where database connections are opened but never returned to the connection pool, eventually exhausting all available connections. The database equivalent...
Connection Pooling
Maintaining a cache of reusable database connections instead of opening a new connection for each request. Dramatically reduces latency (TCP handshakes, TLS...
Consistency
The property that all nodes in a distributed system see the same data at the same time, or that a database transitions only between valid states. One of the...
Convex
A reactive backend platform that combines a real-time database, serverless functions, and file storage into a single TypeScript-native service. Convex...
CRUD
Create, Read, Update, Delete — the four basic operations of persistent storage. Nearly every web application is fundamentally a CRUD app with varying amounts...
Database Connection Pool
A Database Connection Pool is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make...
Database Driver
A Database Driver is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Database Index
A Database Index is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Database Lock
A Database Lock is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Database Migration Detail
A Database Migration Detail is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to...
Database Replication
A Database Replication is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make...
Database Schema
A Database Schema is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Database Sharding
A Database Sharding is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Database Transaction
A Database Transaction is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make...
Database Trigger
A database function that executes automatically in response to INSERT, UPDATE, or DELETE events on a table. Can fire BEFORE (to validate/modify) or AFTER (to...
Document Database
A Document Database is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Drizzle
A TypeScript ORM that positions itself as 'if you know SQL, you know Drizzle.' Unlike Prisma's abstracted query API, Drizzle provides a SQL-like query builder...
DTO
A DTO is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code easier to...
DuckDB
An in-process analytical database (like SQLite for analytics) that runs columnar queries directly on Parquet, CSV, and JSON files without loading them into a...
Ecto
A database toolkit and query DSL for Elixir that provides schemas, changesets for validation, and composable queries without the 'magic' of traditional ORMs....
EdgeDB
A database that combines the reliability of PostgreSQL with a modern query language called EdgeQL, designed to replace both the ORM and raw SQL in application...
Embedded Database
An Embedded Database is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Eventual Consistency
A consistency model where updates will propagate to all nodes eventually, but reads may temporarily return stale data. The price of high availability in...
Indexed Access
An Indexed Access is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
IndexedDB
A low-level browser API for storing large amounts of structured data (including files and blobs) client-side. Unlike localStorage, it's asynchronous, supports...
Index Scan vs Seq Scan
Two fundamental data access methods in databases. An index scan uses a B+ tree index to jump directly to matching rows — fast for selective queries. A...
JDBC
Java Database Connectivity — a standard Java API for connecting to and executing queries against relational databases. Provides a uniform interface regardless...
KV Store
A key-value store — a database or storage system that maps unique keys to arbitrary values, optimized for fast lookups, writes, and deletes by key. Examples...
Left Join
A SQL join that returns all rows from the left (first) table and the matching rows from the right (second) table, filling in NULLs for right-side columns when...
LSM Tree
Log-Structured Merge Tree — a data structure optimized for write-heavy workloads. Writes go to an in-memory buffer (memtable), then flush to sorted, immutable...
Migration
A versioned change to a database schema — adding tables, modifying columns, creating indices. Applied sequentially to evolve the database alongside the code....
MySQL
An open-source relational database management system originally developed by MySQL AB (now Oracle), widely used for web applications and known for its InnoDB...
N+1 Query Problem
A performance anti-pattern where code executes 1 query to fetch a list of N items, then N additional queries to fetch related data for each item. Common with...
Neon
A serverless PostgreSQL platform that separates storage and compute, enabling features impossible with traditional PostgreSQL deployments. Neon's architecture...
NoSQL
A category of databases that don't use traditional relational tables and SQL — including document stores (MongoDB), key-value stores (Redis), column stores...
ORM
Object-Relational Mapping — a technique that lets you interact with a database using your programming language's objects instead of raw SQL. Beloved by those...
Partitioning
Splitting a large table into smaller, more manageable pieces (partitions) based on a key — typically date (range partitioning), category (list partitioning),...
PlanetScale
A serverless MySQL-compatible database platform built on Vitess, the same technology that scales YouTube's database infrastructure. PlanetScale introduced...
Postgres
PostgreSQL — an advanced open-source relational database system known for standards compliance, extensibility, and reliability. The database that doesn't make...
PostgreSQL
PostgreSQL is an open-source, object-relational database management system known for its standards compliance, extensibility, and reliability. Often referred...
Primary Key
A column or combination of columns in a database table that uniquely identifies each row, enforcing both a uniqueness constraint and a NOT NULL constraint. The...
Prisma
A next-generation ORM (Object-Relational Mapping) for Node.js and TypeScript that replaces traditional ORMs with a type-safe database client generated from a...
Query
A request for data from a database or search engine, typically expressed in a structured language like SQL, GraphQL, or a search DSL. As a verb, to query means...
Query Builder
A programmatic API that lets developers construct database queries using method chaining or composable objects instead of writing raw SQL strings. Query...
Query Cache
A mechanism that stores the result set of a previously executed query keyed by the query text (and sometimes its parameters), returning cached results on...
Query Engine
The core component of a database or analytics system responsible for parsing, planning, optimizing, and executing queries against stored data. Query engines...
Query Optimizer
The database subsystem that transforms a parsed SQL query into an efficient execution plan by evaluating strategies like join ordering, index selection, and...
Query Plan
The execution strategy chosen by the database's query optimizer for a SQL statement. Shows which indexes are used, join order and method (nested loop, hash,...
Rails Migration
A Ruby class in Rails that describes a reversible change to the database schema — creating tables, adding columns, building indexes — using a DSL rather than...
Raw SQL
Hand-written SQL statements executed directly against a database, bypassing an ORM or query builder. Developers drop to raw SQL for complex queries,...
RDB
Redis Database file — a compact, point-in-time binary snapshot of the entire Redis dataset written to disk. RDB persistence is configured to trigger after N...
RDBMS
Relational Database Management System — software that stores data in tables of rows and columns, enforces schemas and relational integrity constraints (primary...
Read Replica
A read-only copy of a primary database that receives replicated writes asynchronously (or semi-synchronously), allowing read traffic to be distributed across...
Realm
An embedded, object-oriented mobile database (now part of MongoDB's Atlas Device SDK) that stores data as native objects rather than rows, supports real-time...
Record
A composite data type that groups related values under named fields, typically immutable. In Java 16+, records are concise data carriers. In TypeScript,...
Redis
Redis, short for Remote Dictionary Server, is an open-source, in-memory data structure store used as a database, cache, message broker, and streaming engine....
Replication
The process of copying and maintaining data across multiple database instances or nodes so that every replica holds the same information, improving...
Schema
A formal description of the structure of data — including tables, columns, types, constraints, and relationships in a database, or the shape of JSON, XML, or...
Shard
A horizontal partition of a database or dataset distributed across multiple servers, where each shard holds a subset of rows determined by a sharding key.
Sharding
The strategy of horizontally partitioning data across multiple database instances, each responsible for a subset of the data, to achieve linear scalability and...
Skip List
A probabilistic data structure that maintains a sorted list with multiple levels of linked list shortcuts, enabling O(log n) search, insert, and delete....
SQL
SQL, or Structured Query Language, is the standard language for managing and querying relational databases. Developed at IBM in the 1970s based on Edgar Codd's...
SQLAlchemy
The most widely used Python SQL toolkit and ORM, providing both a low-level Core layer for composing SQL expressions as Python objects and a high-level ORM...
SQL Injection
SQL Injection is a code injection vulnerability that occurs when an attacker inserts malicious SQL statements into input fields or parameters that are...
SQLite
A self-contained, serverless, zero-configuration relational database engine stored as a single file on disk. It is the most widely deployed database in the...
Table
A structured collection of data organized in rows and columns within a relational database, where each row represents a record and each column represents a...
Time-Series Database
A database optimized for storing and querying timestamped data points — metrics, sensor readings, financial ticks. Uses time-based partitioning, compression,...
Tombstone
A marker indicating that a record has been deleted, used instead of physically removing data. Common in distributed databases (Cassandra, DynamoDB) and...
Transaction
A sequence of database operations treated as a single atomic unit — either all succeed (commit) or all are rolled back. Transactions provide ACID guarantees:...
Turso
An edge-hosted database platform built on libSQL (a fork of SQLite) that replicates lightweight SQLite databases to data centers close to users. It gives...
TypeORM
An ORM for TypeScript and JavaScript that maps database tables to classes using decorators, supporting both Active Record and Data Mapper patterns across...
Upsert
An atomic operation that inserts a row if it doesn't exist or updates it if it does, based on a unique key. Eliminates race conditions between separate SELECT...
Vacuum
A PostgreSQL maintenance operation that reclaims storage from dead tuples (rows that were updated or deleted but not yet cleaned up due to MVCC). VACUUM also...
Vector Database
A database optimized for storing and querying high-dimensional vectors (embeddings). Uses approximate nearest neighbor (ANN) algorithms like HNSW or IVF to...
WAL Replay
The crash recovery process where a database reads its write-ahead log from the last checkpoint and re-applies committed transactions that weren't yet written...
Write-Ahead Log
A durability technique where changes are first written to an append-only log before being applied to the main data structure. If the system crashes mid-write,...

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