# Sharding

> A design pattern that splits a dataset across separate stores by a shard key, and routes each request to the shard that holds its key.

Record: `architecture:sharding`
Kind: pattern
Layer: [Performance Core](https://banes-lab.com/records/layer/performance-core.md)
Severity: contextual
Scope: database, storage, messaging
Canonical: https://banes-lab.com/ontology#architecture-sharding

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Load Balancing](https://banes-lab.com/records/architecture/load-balancing.md) and before [Partitioning](https://banes-lab.com/records/architecture/partitioning.md).

## Repair

- Refactored by: Introduce Shard Key, Split Data
- Detected by: hotspot partitions, storage bottleneck
- Violated by: unbounded single partition growth
- Measured by: shard balance, query fan-out
- Enforced by: data architecture review

## Requires

- [Partition Key](https://banes-lab.com/records/lexicon/partition-key.md)

## Reinforces

- [Horizontal Scaling](https://banes-lab.com/records/architecture/horizontal-scaling.md)

## Enables

- [Large Dataset Scaling](https://banes-lab.com/records/lexicon/large-dataset-scaling.md)

## Conflicts with

- [Single Monolithic Store](https://banes-lab.com/records/lexicon/single-monolithic-store.md)

## In tension with

- [Cross-Shard Queries](https://banes-lab.com/records/lexicon/cross-shard-queries.md)

## Tensions

- [Sharding / Cross-Shard Queries](https://banes-lab.com/records/tension/cross-shard-queries-sharding.md)

## Severity

- [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md)

## Category

- [Scalability / Performance / Optimization](https://banes-lab.com/records/architecture-category/scalability-performance-optimization.md)

## Linked from

- [Scalability / Performance / Optimization](https://banes-lab.com/ontology/principles/architecture-category-scalability-performance-optimization.md)
- [Scalability / Performance / Optimization](https://banes-lab.com/ontology/lexicon/lexicon-category-scalability-performance-optimization.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)