In what scenarios is the Copy-on-write technique used to optimize performance or memory management?

Copy-on-write (COW) technique is used to optimize memory usage and improve performance when working with large amounts of data that are rarely modified.

The essence is that when copying an object or data, a full copy is not created immediately. Instead, both variables refer to the same memory location. Actual copying occurs only when one of the copies attempts to modify the data.

Application scenarios:

• In memory management systems, for example, when working with large data structures in iOS, where copying occurs only when modification is necessary.
• When implementing immutable objects to avoid unnecessary copying.
• In file systems and databases to optimize write operations.

Example in iOS: Swift structures (e.g., String, Array) use COW to efficiently manage memory. When you copy an array, the actual data copying does not occur until you modify one of the copies.