Function http_get_bytes_opt 

pub fn http_get_bytes_opt(
    url: &str,
) -> Result<Option<Vec<u8>>, HybridStorageError>

Like http_get_bytes, but a 404 answer is Ok(None) instead of an error: the managed-file engine’s mirror semantics treat 404 as “authoritative absence” (the remote file is GONE, remove the local copy) while every other non-2xx stays an error (keep the local file, retry on a later cycle)..

Errors

Transport failures and non-404 non-2xx statuses map to HybridStorageError::IoError / HybridStorageError::UploadFailed.