# PACELC Theorem

Record: `arch:pacelc-theorem`
Kind: model
Layer: [Causality Core](https://banes-lab.com/records/layer/causality-core.md)
Severity: contextual
Scope: distributed state, consistency, latency
Canonical: https://banes-lab.com/ontology#arch-pacelc-theorem

## Repair

- Refactored by: Decide else-branch latency-vs-consistency per read class (PACELC)
- Detected by: tail latency driven by synchronous cross-region consistency during normal operation
- Violated by: consistency treated as free when the network is healthy, ignoring the latency it costs
- Measured by: latency-vs-staleness tradeoff per read class
- Enforced by: distributed-systems review

## requires

- [CAP Theorem](https://banes-lab.com/records/arch/cap-theorem.md)

## reinforces

- [CAP Theorem](https://banes-lab.com/records/arch/cap-theorem.md)
- [Latency](https://banes-lab.com/records/arch/latency.md)

## enables

- [Latency-Consistency Trade-off When Healthy](https://banes-lab.com/records/lex/latency-consistency-trade-off-when-healthy.md)

## conflicts-with

- [Consistency Assumed Free When Healthy](https://banes-lab.com/records/lex/consistency-assumed-free-when-healthy.md)

## tensions-with

- [Throughput](https://banes-lab.com/records/arch/throughput.md)

## tensions

- [PACELC Theorem Throughput](https://banes-lab.com/records/tension/pacelc-theorem-throughput.md)