Object Pooling & ArrayPool

Allocating a fresh array or object on every call to a hot path is fine for small, occasional use, but it stops being fine when the path runs thousands of times a second and each allocation lives for only a few milliseconds before becoming garbage. The collector keeps up, but it pays for the work, and that work shows up as latency spikes and CPU spent on Gen-0 collections. This lesson covers pooling: renting objects from a shared cache instead of allocating fresh ones, returning them when you're done, and the contract you have to honor for the pattern to be safe. The two pools that show up in modern .NET code are ArrayPool<T> for buffers and the Microsoft.Extensions.ObjectPool family for reusable reference-type instances.