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The CAP theorem states that
a distributed database system can only provide two of three guarantees: Consistency (all nodes see the same data), Availability (every request gets a response), and Partition Tolerance (system works despite network failures). When a network partition occurs, a system must choose between Consistency or Availability.Key Concepts of CAP Theorem:
- Consistency (C): Every read receives the most recent write or an error.
- Availability (A): Every request receives a response (not an error), even if it's not the latest data.
- Partition Tolerance (P): The system continues to operate despite network failures that prevent nodes from communicating.
- The Trade-off: Since network partitions are inevitable in distributed systems, the real choice is between Consistency and Availability (CP vs. AP) during a failure.
System Types:
- CP (Consistency + Partition Tolerance): Prioritizes data accuracy over availability. If a node fails, the system might refuse requests to prevent inconsistent data (e.g., banking systems).
- AP (Availability + Partition Tolerance): Prioritizes uptime. If a node fails, the system allows reads/writes, even if data is outdated or inconsistent (e.g., social media feeds).
- CA (Consistency + Availability): Cannot exist in a distributed system because a system cannot be fully consistent and available without being partition tolerant, which is unrealistic for distributed systems.
The theorem is often used to guide the design of distributed data storage systems like SQL (often CP) versus NoSQL (often AP).
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CAP theorem
Wikipedia
https://en.wikipedia.org › wiki › CAP_theorem
Wikipedia
https://en.wikipedia.org › wiki › CAP_theorem
The CAP theorem, also named Brewer's theorem after computer scientist Eric Brewer, states that any distributed data store can provide at most two of the ...Read more
What Is the CAP Theorem? | IBM
IBM
https://www.ibm.com › think › topics › cap-theorem
IBM
https://www.ibm.com › think › topics › cap-theorem
The CAP theorem says that a distributed system can deliver on only two of three desired characteristics: consistency, availability and partition tolerance.
CAP Theorem for System Design Interviews
Hello Interview
https://www.hellointerview.com › learn › core-concepts
Hello Interview
https://www.hellointerview.com › learn › core-concepts
Consistency: All nodes see the same data at the same time. When a write is made to one node, all subsequent reads from any node will return that updated value.Read more
CAP Theorem Explained: Consistency, Availability & ...
BMC Software
https://www.bmc.com › blogs › cap-theorem
BMC Software
https://www.bmc.com › blogs › cap-theorem
30 Oct 2024 — The CAP theorem maintains that when a distributed database experiences a network failure, you can provide either consistency or availability.Read more
What is the CAP Theorem?
Hazelcast
https://hazelcast.com › distributed-computing › cap-the...
Hazelcast
https://hazelcast.com › distributed-computing › cap-the...
CAP theorem states that a distributed computer system can, at best, provide only 2 of the 3 properties: Consistency, Availability, and Partition tolerance.
Understanding the CAP Theorem: Balancing Consistency ...
Medium · Neha Gupta
300+ likes · 2 years ago
Medium · Neha Gupta
300+ likes · 2 years ago
The CAP theorem states that it is not possible to guarantee all three of the desirable properties — consistency, availability, and partition ...Read more
ELI5: CAP Theorem in System Design : r/softwarearchitecture
Reddit · r/softwarearchitecture
9 comments · 10 months ago
Reddit · r/softwarearchitecture
9 comments · 10 months ago
The CAP Theorem states that in a distributed system, you need to decide whether you want consistency or availability. You cannot have both.Read more
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Web results
CAP Theorem: One of the Most Misunderstood Terms
ByteByteGo
https://bytebytego.com › guides › cap-theorem-one-of-t...
ByteByteGo
https://bytebytego.com › guides › cap-theorem-one-of-t...
CAP theorem states that a distributed system can't provide more than two of these three guarantees simultaneously.Read more
The CAP Theorem in DBMS
GeeksforGeeks
https://www.geeksforgeeks.org › dbms › the-cap-theore...
GeeksforGeeks
https://www.geeksforgeeks.org › dbms › the-cap-theore...
6 Dec 2025 — The CAP theorem states that distributed databases can have at most two of the three properties: consistency, availability, and partition tolerance.Read more
An Illustrated Proof of the CAP Theorem
GitHub
https://mwhittaker.github.io › blog › an_illustrated_proo...
GitHub
https://mwhittaker.github.io › blog › an_illustrated_proo...
The CAP theorem states that a distributed system cannot simultaneously be consistent, available, and partition tolerant.Read more
CAP theorem
In database theory, the CAP theorem, also named Brewer's theorem after computer scientist Eric Brewer, states that any distributed data store can provide at most two of the following three guarantees:
Consistency
Every read receives the most recent write or an error.WikipediaMoreLessDescription