Type Alias SpillHandle 

pub type SpillHandle = Arc<Mutex<File>>;

A shared, mutex-guarded handle to the spill file used in durable mode.

Multiple async tasks may hit a full channel simultaneously; the Mutex serialises their appends without data loss.

ponytail: global Mutex over the file — upgrade to a dedicated spill-writer task if append throughput under sustained backpressure becomes the bottleneck.

Aliased Type

pub struct SpillHandle { /* private fields */ }