CAP Theorem

Question 1

What is CAP Theorem? Why is it important?

Answer 1

CAP theorem states that a distributed system can only fulfill two of the following three requirements:

• Consistency
• Availability
• Partition Tolerence

All three are impoerant factors in a distributed system, but you have to evaluate trade-offs depending on your requirements.

Question 2

Which aspect of CAP Theorem cannot typically be compromised?

Answer 2

Partition tolerance cannot be ignored as, by nature, if the system has multiple partitions and one fails, it will compromise both availability and consistency.

Question 3

In practical terms, which two options are the choices when building a distributed system?

Answer 3

Either consistency or availability must be prioritized.

Question 4

When building a system that needed to prioritize availability and consistency, which would database type might you choose?

Answer 4

Since you don’t need partition tolerence, a relational database would be a good choice.

Question 5

In a system that prioritized both consistency and partition tolerance, which database store would be a good option?

Answer 5

A distributed store like BigTable or Hbase has strong consistency guarantees while retaining partition intolerance.

Question 6

What type of database might be used in a system that prioritizes availability with partition tolerance?

Answer 6

Potentially a columnar store such as Cassandra or a document store like MongoDB, which doesn’t have as strict consistency requirements but is distributed and highly available.