The CAP theorem in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the CAP theorem stand for in distributed systems?

CAP stands for Consistency, Availability, and Partition tolerance. It describes the trade-offs in distributed systems where you can only guarantee two of these three properties at the same time.

beginner

Define Consistency in the context of the CAP theorem.

Consistency means every read receives the most recent write or an error. All nodes see the same data at the same time, like everyone reading the same page in a book.

beginner

What does Availability mean in the CAP theorem?

Availability means every request gets a response, even if some nodes fail. The system is always ready to serve data, like a store that never closes.

beginner

Explain Partition tolerance in simple terms.

Partition tolerance means the system keeps working even if network parts can't talk to each other. Like two teams working separately when the phone line is down.

intermediate

Why can't a distributed system guarantee all three CAP properties at once?

Because when a network split happens (partition), the system must choose between being consistent or available. It can't be both at the same time due to communication limits.

Which two properties can a distributed system guarantee simultaneously according to the CAP theorem?

A Consistency and Availability

B Availability and Partition tolerance

C Consistency and Partition tolerance

D All three at the same time

A system can guarantee Consistency and Partition tolerance or Availability and Partition tolerance but may sacrifice the third property during network partitions.

What happens to Availability during a network partition if the system chooses Consistency?

A Availability is maintained fully

B Availability may be lost temporarily

C Availability improves

D Availability is unrelated to Consistency

Choosing Consistency during a partition means some requests may not be served, reducing Availability temporarily.

Partition tolerance means:

A The system always returns the latest data

B The system stops working during network failures

C The system continues despite network splits

D The system is always available

Partition tolerance means the system keeps functioning even if parts of the network can't communicate.

Which CAP property ensures all nodes see the same data at the same time?

A Latency

B Partition tolerance

C Availability

D Consistency

Consistency ensures all nodes have the same data view simultaneously.

If a system prioritizes Availability and Partition tolerance, what might it sacrifice?

A Consistency

B Latency

C Security

D Scalability

Choosing Availability and Partition tolerance may lead to temporary inconsistencies.

Explain the CAP theorem and its significance in distributed system design.

Think about how a network split affects system behavior.

Describe scenarios where a system might choose Consistency over Availability, and vice versa.

Consider what matters more: always correct data or always responsive system.