---
title: "ACID"
description: "ACID is an acronym describing four properties — Atomicity, Consistency, Isolation, and Durability — that guarantee database transactions are processed reliably."
canonical: "https://motherduck.com/glossary/acid/"
related:
  - title: "DuckLake Architecture Deep Dive"
    url: "https://motherduck.com/blog/ducklake-architecture-deep-dive/"
  - title: "Database Concepts | MotherDuck Docs"
    url: "https://motherduck.com/docs/concepts/database-concepts/"
  - title: "DuckDB breaks the lakehouse? ft. Daniel Beach | EXPLAIN ANALYZE | MotherDuck"
    url: "https://motherduck.com/explain-analyze/0003-duckdb-breaks-the-lakehouse/"
gated_asset:
  title: "DuckLake on MotherDuck"
  url: "https://motherduck.com/product/ducklake/"
---

# ACID

> ACID is an acronym describing four properties — Atomicity, Consistency, Isolation, and Durability — that guarantee database transactions are processed reliably.

## Overview

ACID is shorthand for four guarantees that a transactional database makes about how it processes work. Together they ensure that transactions behave predictably even in the presence of concurrent access, crashes, or hardware failures.

## The Four Properties

- **Atomicity** — a transaction's operations either all succeed or none do; there's no partial commit.
- **Consistency** — a transaction moves the database from one valid state to another, respecting constraints, types, and referential integrity rules.
- **Isolation** — concurrent transactions don't see each other's uncommitted changes; the effective isolation level determines exactly what anomalies are prevented.
- **Durability** — once a transaction commits, its changes survive crashes and power loss, typically because they were written to a write-ahead log before the commit was acknowledged.

## Why ACID Matters

ACID guarantees are what make it safe to build applications on top of a shared database without reasoning about every possible interleaving of concurrent operations. Without them, a crash mid-write or two simultaneous updates could silently corrupt or lose data.

## ACID in DuckDB

DuckDB is a fully ACID-compliant database. It implements a variant of MVCC inspired by the HyPer research system, tailored for hybrid analytical workloads: updates are applied in place and prior versions are kept in an undo buffer so concurrent readers and writers don't block each other. Durability is provided by a write-ahead log that records changes before they're applied to the main database file, and `CHECKPOINT` periodically merges the WAL into the database file. Because DuckDB uses optimistic concurrency control, isolation is enforced by aborting a transaction with a conflict error if it tries to commit changes that overlap with another transaction's writes, rather than by blocking with locks.