Revision Notes/System Design Concepts
Field Entry - System Design Concepts
CAP Theorem
In a distributed system, you can only guarantee two out of three: Consistency, Availability, and Partition Tolerance.
Field Note - Real-world Analogy
“Imagine a Google Doc being edited by two people with an unstable internet connection. Consistency: the doc shows the same content to both users at all times — but if the internet drops, one user might be blocked from editing until connection restores. Availability: both users can keep editing even offline — but when they reconnect, there might be conflicts to resolve.”
Field Observations - Key Topics Covered
Consistency (C) means every read gets the most recent write or an error. If you write a value on Node A, anyone reading from Node B immediately sees that new value. There is a single, consistent view of the data across all nodes at all times.
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