Type Alias SpendingLock 

pub type SpendingLock = Arc<Mutex<()>>;

Lock that serializes spending operations (createAction). Non-spending endpoints (encrypt, getPublicKey, listOutputs, etc.) are unaffected.

Why: With limited UTXOs, concurrent createAction calls race on SQLite’s write lock and the loser gets SQLITE_BUSY_SNAPSHOT instead of waiting for the winner’s change output. This lock queues them so each spending request sees the previous one’s change.

Aliased Type

pub struct SpendingLock { /* private fields */ }