# Ordering Key or Sequence

> The requirement that each event carry a key or sequence number that fixes its position in order.

Record: `lex:ordering-key-or-sequence`
Kind: constraint
Layer: [Causality Core](https://banes-lab.com/records/layer/causality-core.md)
Canonical: https://banes-lab.com/ontology/lexicon#lex-ordering-key-or-sequence

## category

- [Causality / Ordering / Distributed Time](https://banes-lab.com/records/lex-category/causality-ordering-distributed-time.md)

## referenced-by

- [Event Ordering](https://banes-lab.com/records/arch/event-ordering.md)