---
title: "Brewer’s Conjecture and the Feasibility of Consistent, Available, Partition-Tolerant Web Services"
description: "The CAP theorem asks what a replicated service can promise when the network splits. Read it to see how one completed write and one later isolated read force an exact choice: answer from incomplete knowledge or wait for communication that may never return."
canonical_url: "https://fanout.sh/daily/2026-08-31-cap-theorem"
md_url: "https://fanout.sh/daily/2026-08-31-cap-theorem.md"
last_updated: "2026-08-31"
access: "public"
---

# Brewer’s Conjecture and the Feasibility of Consistent, Available, Partition-Tolerant Web Services

The CAP theorem asks what a replicated service can promise when the network splits. Read it to see how one completed write and one later isolated read force an exact choice: answer from incomplete knowledge or wait for communication that may never return.

## Paper details

- Authors: Seth Gilbert and Nancy Lynch

- Venue: ACM SIGACT News 2002

- Track: Systems

- Difficulty: Very Easy

- Reading time: 30 min

- Original paper: https://doi.org/10.1145/564585.564601

## What you will learn

- How the paper defines atomic consistency, availability, and partition tolerance for one distributed read/write object.

- Why an isolated replica cannot distinguish a delayed write from a missing one, so answering now can be stale while waiting breaks termination.

- Why timeouts and weaker consistency create practical policies without restoring all three guarantees under the theorem's assumptions.

## Continue exploring

[Explore consistency models in Fanout](https://fanout.sh/system/archive/consistency-models): Continue into Fanout's consistency guide and compare linearizability, sequential, causal, session, and eventual guarantees against real product invariants.

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