Readfirst

Readfirst is an informal term used in software engineering to describe techniques, conventions, or components that give priority to read operations, or that perform a read before a write within a given sequence of actions. The exact meaning is context-dependent and can vary by project or domain.

In concurrency control, read-first or read-first protocols describe approaches that allow readers to access data before ongoing updates are completed. This can reduce read latency and improve throughput, but may expose readers to stale or intermediate states. The precise guarantees depend on the specific protocol, such as read locks, timestamp ordering, or multi-version concurrency control (MVCC).

In versioned data stores and MVCC systems, read-first semantics often mean that readers observe a stable, previously committed version while a writer creates a new version. This helps ensure consistent reads even as updates occur, at the cost of temporarily diverging from the latest uncommitted write.

In programming libraries and APIs, readfirst may be used as a naming pattern for methods that first retrieve an existing value before deciding to modify or insert one. For example, a get-or-create operation may reflect a read-first step before a potential write.

Because readfirst is not a standardized term, its interpretation is highly dependent on the surrounding technology and documentation. Related concepts include read-write locks, MVCC, and optimistic concurrency control.