Lesson 142
Distributed Systems & the CAP Theorem
Why a partition forces a choice
1:00Why spreading work across many machines is hard, and how the CAP theorem and PACELC frame the fundamental trade-offs every distributed system must make.
By the end, you can
- Explain the three motivations for distributed systems and the three core difficulties they introduce.
- Identify the first two of the eight fallacies and explain why they are dangerous.
- Trace what happens to a read during a network partition under a CP system versus an AP system.
- State the CAP theorem precisely and explain why "CA" is not a practical option.
- Debunk the "pick 2 of 3" misreading of CAP.
- Read a PACELC label (e.g. PA/EL) and explain what trade-offs the system makes both during and outside a partition.
- Rank strong, causal, and eventual consistency from strongest to weakest and describe what each guarantees.
- Distinguish at-most-once, at-least-once, and exactly-once delivery semantics.
- Describe how an idempotency pattern achieves effectively exactly-once behaviour under at-least-once delivery.
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