itemKey

An itemKey is a value used to uniquely identify an item within a collection. It provides a stable reference that remains linked to the item through updates, moves, or deletions. In data models, an itemKey often corresponds to a primary key in a database, typically a numeric identifier or a globally unique identifier (GUID/UUID). It can be a natural key derived from the data or a surrogate key introduced to ensure stability and immutability.

In user interface frameworks, itemKey is used to track items in lists so that the rendering engine can efficiently update only the parts of the UI that change. A stable key helps preserve item state and reduces unnecessary re-renders when the list data changes. Keys are commonly simple data values such as strings or numbers and should remain constant for the lifetime of the item.

In data structures and APIs, the itemKey functions as the map key or index used for efficient retrieval, updates, and integrity checks. For caches and storage systems, the itemKey enables quick lookups and ensures that operations target the correct item.

Design considerations for itemKey include ensuring uniqueness, immutability, and stability over time. Surrogate keys are often favored for mutable datasets, while natural keys can be used when they remain stable and unique. Key selection should avoid including sensitive or changing information, and keys should be sized appropriately for performance and storage.

Common pitfalls include changing a key after creation, which can break references or undo prior updates; duplicate keys that corrupt lookups; and using highly derived or long keys that increase memory or serialization costs.

See also: primary key, surrogate key, natural key, key-value store, and hash function.