Side by side
ACIDvsBASE
What is the difference between ACID and BASE?
Updated 3 min read7 differences
In short
ACID makes every transaction correct and visible at once; BASE lets replicas briefly disagree so the system stays available and scales across servers.
ACID
Atomicity, Consistency, Isolation, Durability
ACID is a set of four guarantees, atomicity, consistency, isolation, and durability, that keep database transactions reliable even when errors or crashes occur.
Read the page on ACIDBASE
Basically Available, Soft state, Eventually consistent
BASE describes distributed databases that favor availability over immediate consistency: they keep answering and let copies of data briefly disagree.
Read the page on BASEACID and BASE compared
| Aspect | ACID | BASE |
|---|---|---|
| Stands for | Atomicity, consistency, isolation, durability | Basically available, soft state, eventually consistent |
| Priority | Correctness of every transaction | Availability and scale |
| After a write | Committed data is visible right away | Replicas may return the old value for a while |
| When the network splits | May refuse or delay requests to stay correct | Keeps answering, possibly with stale data |
| Scaling | Simplest on one server; harder across many | Designed to spread across many servers and regions |
| Typical systems | PostgreSQL, MySQL, SQLite, distributed SQL databases | Cassandra, DynamoDB by default, DNS, caches |
| Best for | Payments, orders, inventory and bookings | Feeds, counters, catalogs, sensor data and analytics |
The difference, explained
ACID and BASE are two sets of promises a database can make about your data. ACID, short for atomicity, consistency, isolation and durability, promises that each transaction happens completely or not at all, follows the database's rules, doesn't see other transactions' unfinished work and survives a crash once committed. BASE, short for basically available, soft state, eventually consistent, promises less: the system keeps answering, and replicas that briefly disagree will converge once writes stop.
The difference exists because of distribution. On one server, ACID is relatively cheap. Across many servers and data centers, keeping every copy in agreement before answering means waiting for the network, and when the network between servers fails, the system must choose between refusing requests and serving possibly stale data. ACID systems choose correctness and may slow down or reject writes; BASE systems, such as Apache Cassandra or Amazon DynamoDB in their default modes, choose availability and let copies catch up in the background.
The right model depends on what a brief inconsistency would cost. A bank transfer, a stock count or a seat reservation needs ACID, because two users must never both get the last item. A like counter, a social feed, a product catalog or DNS can live with a few seconds of disagreement, which BASE trades for speed and resilience. Many systems mix both: orders go to an ACID database, while caches, search indexes and analytics copies are eventually consistent.
A common misconception is that SQL means ACID and NoSQL means BASE. Many NoSQL databases, including MongoDB, DynamoDB and Cassandra, now offer transactions or stronger consistency levels per request, and distributed SQL databases provide ACID across many servers. Another is confusing the C in ACID, which means data obeys the database's rules, with the C in the CAP theorem, which means every node returns the latest write.
Which one should you use?
Choose ACID when…
- Money, stock levels or bookings change, and a conflict must never slip through.
- Several related writes must succeed or fail together.
- Users must see their own change right after they make it.
- Your data fits on one primary server or in a distributed SQL database.
Choose BASE when…
- The system must keep accepting reads and writes even when servers or links fail.
- Data is spread across many servers or regions and must scale out cheaply.
- A few seconds of stale data, such as an old like count, does no harm.
- Writes are huge in volume and rarely conflict, such as events, logs or sensor readings.
Readers ask
Is BASE the opposite of ACID?
Not strictly. The names are a chemistry pun, but the two are ends of a spectrum, and many databases let you pick a stronger or weaker consistency level per request.
Are NoSQL databases ACID compliant?
Some are. MongoDB supports multi-document ACID transactions, and DynamoDB and Cassandra offer transactions or strong consistency options with limits, so check what each database guarantees and at what cost.
What does eventually consistent mean in practice?
After a write, some readers may still see the old value for a short time, usually milliseconds to seconds. Once updates stop, every replica returns the same value.