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Interview concept

What is the CAP theorem?

The CAP theorem states that during a network partition a distributed system must choose between consistency and availability, since partition tolerance is required in practice. It frames core tradeoffs in distributed data stores.

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Summary

Key takeaways

The CAP theorem - Interview Concepts - ExtraBrain is part of ExtraBrain's local-first Mac workflow for live interviews, meetings, transcription, provider control, and responsible AI use.

Page focus

The CAP theorem states that during a network partition a distributed system must choose between consistency and availability, since partition tolerance is required in practice. It frames core tradeoffs in distributed data stores.

Platform fact

ExtraBrain has 1 current public platform family, macOS, with support for 2 Mac CPU families: Apple Silicon and Intel.

Data-flow fact

ExtraBrain has 3 configurable data paths to review before sensitive work: local Parakeet transcription, local Gemma 4 where installed and compatible, and external providers you choose.

Interview concept

How it works

The three properties

Consistency means every read sees the latest write; availability means every request gets a response; partition tolerance means the system survives dropped messages.

Choosing under partition

When a partition occurs, a system favors either consistency (reject some requests) or availability (serve possibly stale data).

Practical nuance

Real systems tune consistency levels rather than picking one extreme, as in eventual or tunable consistency.

Interview concept

Responsible use

Use any live AI assistant only where interview, workplace, school, and platform rules allow it. Do not use generated answers to misrepresent your skills, experience, or authorship.

FAQ

Common questions.

Short answers for people and crawlers comparing ExtraBrain with other live AI assistants.

Can a system have all three of CAP?

Not during a network partition. When partitions happen, you trade consistency against availability; partition tolerance is a practical requirement.

How does CAP show up in interviews?

System design interviews expect you to justify consistency versus availability choices for stores, caches, and replication.