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Question 13 of 51

Why is it impossible to achieve all three properties of CAP simultaneously in a distributed system?

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It's impossible because of the fundamental nature of network partitions in distributed systems. When a network partition occurs (nodes cannot communicate), you face a choice:

  1. Choose Consistency: Stop serving requests on partitioned nodes to maintain data consistency. This sacrifices availability.
  2. Choose Availability: Continue serving requests on all nodes, but risk serving stale data, sacrificing consistency.

You cannot have both because:

  • To maintain consistency during a partition, you must either reject requests (losing availability) or wait for network healing (also losing availability)
  • To maintain availability, you must serve requests with potentially stale data (losing consistency)

Partition tolerance is mandatory in distributed systems because network failures are inevitable.

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