# Lost Update

> A defect in which concurrent writers overwrite each other's changes without a version check.

Record: `architecture:lost-update`
Kind: anti-pattern
Layer: [Enforcement Core](https://banes-lab.com/records/layer/enforcement-core.md)
Severity: discouraged
Scope: state_transaction
Aliases: Whole-File Write Race
Canonical: https://banes-lab.com/ontology#architecture-lost-update

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Silent Data Corruption](https://banes-lab.com/records/architecture/silent-data-corruption.md) and before [Dual Write](https://banes-lab.com/records/architecture/dual-write.md).

## Repair

- Refactored by: [optimistic_locking](https://banes-lab.com/records/architecture/optimistic-locking.md), [pessimistic_locking](https://banes-lab.com/records/architecture/pessimistic-locking.md), merge_policy, transaction_isolation
- Detected by: last_write_wins_without_version, no_optimistic_lock, concurrent_update_defects
- Violated by: Allow concurrent writers to overwrite each other without version checks, locks, compare-and-swap, or transaction isolation.
- Measured by: concurrent update conflicts found in tests
- Enforced by: optimistic-locking checks, concurrency tests

## Severity

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

## Category

- [Anti-patterns](https://banes-lab.com/records/architecture-category/anti-patterns.md)

## Force

- [State transaction](https://banes-lab.com/records/force/state-transaction.md)

## Negated by

- [Write Barrier](https://banes-lab.com/records/architecture/write-barrier.md)
- [Concurrency Control](https://banes-lab.com/records/architecture/concurrency-control.md)

## Linked from

- [Shared surfaces](https://banes-lab.com/pag/orchestration/shared-surfaces.md)
- [Coordination is software](https://banes-lab.com/disciplined-methodology/collaborate/coordination-is-software.md)
- [Seven controls, seven classes](https://banes-lab.com/software-architecture/decay/seven-controls-seven-classes.md)
- [Anti-patterns](https://banes-lab.com/ontology/principles/architecture-category-anti-patterns.md)
- [Coordination Surfaces](https://banes-lab.com/ontology/principles/architecture-category-coordination-surfaces.md)
- [Transactions / State / Concurrency](https://banes-lab.com/ontology/principles/architecture-category-transactions-state-concurrency.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The forces](https://banes-lab.com/ontology/schema/the-forces.md)