# Platform Notes > USearch for Mojo ### What This Binding Does Not Expose - __Progress on loads, saves, absorbs and splits.__ Their entry points take no config, so those calls run without a handler. - __Deferred cursors and streams.__ `DenseIndexDeferredOn` offers neither, since their pulls block. ### Design - __A thin layer over the C ABI.__ Every name follows `c/usearch/`: a C verb `usearch_dense_` is a `` here, and enums mirror C enums, never strings. - __Pointers keep their types and their borrows.__ A C pointer that may be null is an `Optional[Pointer]`, a view carries the origin of what it borrows into its pointer, and only opaque handles and `void *` state cross as an integer `Address`. - __The receiver chooses, the verb stays.__ The index runs a verb on the calling thread, `on(executor)` blocks on an executor, and `deferred(executor)` submits it, all with the same arguments. - __Deferred calls use the language's own idioms.__ `status` polls through `usearch_outcome_status`, `wait` blocks through `usearch_outcome_wait`, and the origins a `Deferred` carries keep everything it borrows alive until it is gone. - __No life of its own.__ The binding starts no threads and keeps no queues; releasing a `Deferred` rides Mojo's destruction at last use, which waits for the call first. - __Arenas are lent and reused, never shared.__ Every output whose length scales with the call lands in an arena the caller passes; the binding stamps each arena with a counter that every view checks before reading, and keeps no call counts. - __Nothing costs anything until it is used.__ Submitting a call allocates nothing, and an arena allocates only when a call writes into it. - __Blocking calls live on the stack.__ A blocking call keeps its outcome and outputs in stack slots and allocates nothing of its own; a deferred one moves those slots to one heap allocation it frees once final. - __`ScalarKind`, not `Scalar`.__ Types drop `usearch_` and `_t` from their C names, except `ScalarKind`, which keeps clear of Mojo's built-in `Scalar`.