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Advanced Topic 44 of 51 Databases

CAP Theorem

Trade-off among consistency, availability and partition tolerance.

How it works

When a network partition occurs, a distributed system must choose between consistency (all nodes see the same data) and availability (every request gets a response). Partition tolerance is not optional.

Where it is used

Choosing CP or AP databases.

Common pitfall

CAP is not a menu of any two; PACELC adds latency trade-offs when no partition exists.

Where it fits in the course

CAP Theorem is topic 44 of 51 in Databases, rated Advanced. It follows Graph Databases. The next topic is Eventual Consistency.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Databases quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is CAP Theorem?
Trade-off among consistency, availability and partition tolerance. It belongs to Databases and is an advanced-level topic.
Where do people use CAP Theorem?
Choosing CP or AP databases.
What is the most common mistake with CAP Theorem?
CAP is not a menu of any two; PACELC adds latency trade-offs when no partition exists.
What should I learn before this topic?
Start with Graph Databases, the topic just before it in Databases.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Databases quiz.
Is CAP Theorem hard to learn?
It is an Advanced topic. Expect to read the explanation more than once and to connect it with earlier topics. Working through a small example by hand helps most.
How long does it take to learn CAP Theorem?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to CAP Theorem?
Graph Databases, Eventual Consistency, Column-Family Stores are closely connected. The full list is in the related topics section of this page.
What should I study after CAP Theorem?
Continue with Eventual Consistency, the next topic in Databases.

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