diff --git a/dynamiq/clients/dynamiq.py b/dynamiq/clients/dynamiq.py
index 3541f64e5..3bf97c270 100644
--- a/dynamiq/clients/dynamiq.py
+++ b/dynamiq/clients/dynamiq.py
@@ -1,4 +1,8 @@
 import asyncio
+import atexit
+import threading
+import weakref
+from queue import SimpleQueue
 from typing import TYPE_CHECKING, Any
 from urllib.parse import urljoin
 
@@ -19,6 +23,8 @@
 
 DYNAMIQ_BASE_URL = "https://collector.getdynamiq.ai"
 
+_FLUSH_TIMEOUT = 0.5  # seconds to wait for remaining traces on shutdown
+
 
 class HttpBaseError(Exception):
     pass
@@ -45,6 +51,62 @@ def __init__(self, base_url: str | None = None, access_key: str | None = None, t
             raise ValueError("No API key provided")
         self.timeout = timeout
 
+        # Background queue and thread for non-blocking sync trace dispatch
+        self._trace_queue: SimpleQueue[list["Run"] | None] = SimpleQueue()
+        self._bg_thread = threading.Thread(target=self._trace_worker, daemon=True)
+        self._bg_thread.start()
+        atexit.register(self.close)
+
+        # Lazily initialised async HTTP client (reused across calls).
+        # Both the lock and the client are bound to a specific event loop;
+        # we track the loop via weakref so we can detect when it changes
+        # (e.g. successive asyncio.run() calls in a test suite).
+        self._async_client: httpx.AsyncClient | None = None
+        self._async_client_lock: asyncio.Lock | None = None
+        self._async_client_loop: weakref.ref | None = None
+        self._async_init_mutex = threading.Lock()  # guards loop-change detection
+
+    # ------------------------------------------------------------------
+    # Background worker
+    # ------------------------------------------------------------------
+
+    def _trace_worker(self) -> None:
+        """Drain *_trace_queue* in a background daemon thread."""
+        while True:
+            runs = self._trace_queue.get()
+            if runs is None:  # sentinel -> shut down
+                break
+            self._send_traces_sync(runs)
+
+    def close(self) -> None:
+        """Flush pending traces and stop the background thread."""
+        self._trace_queue.put(None)  # send sentinel
+        self._bg_thread.join(timeout=_FLUSH_TIMEOUT)
+        # Best-effort async client cleanup
+        client = self._async_client
+        if client is not None and not client.is_closed:
+            try:
+                loop = asyncio.get_running_loop()
+                loop.create_task(client.aclose())
+            except RuntimeError:
+                # No running loop - run synchronously in a fresh loop
+                try:
+                    asyncio.run(client.aclose())
+                except Exception:  # nosec B110
+                    pass
+            self._async_client = None
+
+    async def aclose(self) -> None:
+        """Async counterpart of *close()* - shuts down the async HTTP client."""
+        client = self._async_client
+        if client is not None and not client.is_closed:
+            await client.aclose()
+            self._async_client = None
+
+    # ------------------------------------------------------------------
+    # Sync transport
+    # ------------------------------------------------------------------
+
     def _send_traces_sync(self, runs: list["Run"]) -> None:
         """Synchronous method to send traces using requests"""
         try:
@@ -66,12 +128,60 @@ def _send_traces_sync(self, runs: list["Run"]) -> None:
         except Exception as e:
             logger.error(f"Failed to send traces (sync). Error: {e}")
 
+    # ------------------------------------------------------------------
+    # Async transport
+    # ------------------------------------------------------------------
+
+    def _is_same_loop(self, loop: asyncio.AbstractEventLoop) -> bool:
+        """Check if *loop* is the same event loop we last bound to."""
+        if self._async_client_loop is None:
+            return False
+        prev = self._async_client_loop()  # dereference weakref
+        return prev is loop
+
+    async def _get_async_client(self) -> httpx.AsyncClient:
+        """Return a shared *httpx.AsyncClient*, creating it lazily.
+
+        The lock and client are bound to the current event loop.  When the
+        loop changes (e.g. a new ``asyncio.run()``), both are recreated so
+        we never use an ``asyncio.Lock`` from a dead loop.
+        """
+        current_loop = asyncio.get_running_loop()
+
+        # Fast path - same loop, client alive
+        if (
+            self._async_client is not None
+            and not self._async_client.is_closed
+            and self._is_same_loop(current_loop)
+        ):
+            return self._async_client
+
+        # Slow path - need to (re)create lock and/or client
+        with self._async_init_mutex:
+            # Loop changed -> discard old lock (bound to old loop) and client
+            if not self._is_same_loop(current_loop):
+                old_client = self._async_client
+                if old_client is not None and not old_client.is_closed:
+                    try:
+                        await old_client.aclose()
+                    except Exception:  # nosec B110
+                        pass
+                self._async_client = None
+                self._async_client_lock = asyncio.Lock()
+                self._async_client_loop = weakref.ref(current_loop)
+
+        # Now acquire the (loop-local) async lock for client creation
+        async with self._async_client_lock:  # type: ignore[union-attr]
+            if self._async_client is None or self._async_client.is_closed:
+                self._async_client = httpx.AsyncClient()  # nosec B113
+        return self._async_client
+
     async def request(self, method: str, url_path: URLTypes, **kwargs: Any) -> Response:
         logger.debug(f'[{self.__class__.__name__}] REQ "{method} {url_path}". Kwargs: {kwargs}')
         url = f"{self.base_url}/{str(url_path).lstrip('/')}" if self.base_url else str(url_path).lstrip("/")
         try:
-            async with httpx.AsyncClient() as client:  # nosec B113
-                response = await client.request(method, url=url, timeout=self.timeout, **kwargs)
+            client = await self._get_async_client()
+            response = await client.request(method, url=url, timeout=self.timeout, **kwargs)
         except (httpx.TimeoutException, httpx.NetworkError) as e:
             raise HttpConnectionError(e) from e
 
@@ -105,6 +215,10 @@ async def _send_traces_async(self, runs: list["Run"]) -> None:
         except Exception as e:
             logger.error(f"Failed to send traces (async). Error: {e}")
 
+    # ------------------------------------------------------------------
+    # Public interface
+    # ------------------------------------------------------------------
+
     def trace(self, runs: list["Run"]) -> None:
         """Sync method required by BaseTracingClient interface"""
         if not runs:
@@ -115,6 +229,6 @@ def trace(self, runs: list["Run"]) -> None:
                 loop = asyncio.get_running_loop()
                 loop.create_task(self._send_traces_async(runs))
             else:
-                self._send_traces_sync(runs)
+                self._trace_queue.put(runs)
         except Exception as e:
             logger.error(f"Failed to send traces. Error: {e}")
diff --git a/dynamiq/flows/flow.py b/dynamiq/flows/flow.py
index 26347f3ff..d340eefee 100644
--- a/dynamiq/flows/flow.py
+++ b/dynamiq/flows/flow.py
@@ -316,8 +316,10 @@ def run_sync(self, input_data: Any, config: RunnableConfig = None, **kwargs) ->
                     self._results.update(results)
                     self._ts.done(*results.keys())
 
-                    # Wait for ready nodes to be processed and reduce CPU usage
-                    time.sleep(0.003)
+                    if not results:
+                        # Yield CPU only when no futures completed; futures.wait
+                        # already blocks when work is in progress.
+                        time.sleep(0.003)
 
                 run_executor.shutdown()