diff --git a/web_api/app/alignment.py b/web_api/app/alignment.py
index e3d52a9da..ec3350cfb 100644
--- a/web_api/app/alignment.py
+++ b/web_api/app/alignment.py
@@ -1,9 +1,11 @@
 # pylint: disable=import-error
+import asyncio
 import base64
 import gzip
 import io
 import json
 import struct
+import threading
 import time
 
 import numpy as np
@@ -37,6 +39,9 @@ def _get_misd_detector():
 
 api = FastAPI()
 
+# Limits concurrent GPU computations to 1; additional requests queue asynchronously.
+_gpu_semaphore = asyncio.Semaphore(1)
+
 
 @api.exception_handler(Exception)
 async def generic_handler(request: Request, exc: Exception):
@@ -455,23 +460,47 @@ async def apply_correspondences(request: Request):
     )
     print(f"[apply_correspondences] params: {params}")
 
-    t0 = time.time()
-    relaxed_field, warped_image = apply_correspondences_to_image(
-        correspondences_dict=correspondences_dict,
-        image=image_tensor,
-        src_mask=src_mask_tensor,
-        tgt_mask=tgt_mask_tensor,
-        tgt_image=tgt_image_tensor,
-        **params,
-    )
-    t_corr = time.time() - t0
-    print(f"[apply_correspondences] correspondence relaxation: {t_corr:.2f}s")
-
-    misd_as_input = None
-    if tgt_image_tensor is not None:
-        misd_as_input = _run_misd_detection(warped_image, tgt_image_tensor, image_tensor.dtype)
-
-    print(f"[apply_correspondences] total: {time.time() - t0:.2f}s")
+    cancel_event = threading.Event()
+
+    def _run_computation():
+        t0 = time.time()
+        relaxed_field, warped_image = apply_correspondences_to_image(
+            correspondences_dict=correspondences_dict,
+            image=image_tensor,
+            src_mask=src_mask_tensor,
+            tgt_mask=tgt_mask_tensor,
+            tgt_image=tgt_image_tensor,
+            cancel_event=cancel_event,
+            **params,
+        )
+        t_corr = time.time() - t0
+        print(f"[apply_correspondences] correspondence relaxation: {t_corr:.2f}s")
+
+        misd_as_input = None
+        if tgt_image_tensor is not None:
+            misd_as_input = _run_misd_detection(warped_image, tgt_image_tensor, image_tensor.dtype)
+
+        print(f"[apply_correspondences] total: {time.time() - t0:.2f}s")
+        return relaxed_field, warped_image, misd_as_input
+
+    async with _gpu_semaphore:
+        if await request.is_disconnected():
+            print("[apply_correspondences] Client disconnected while waiting in queue")
+            return Response(status_code=499)
+
+        compute_task = asyncio.get_event_loop().run_in_executor(None, _run_computation)
+
+        # Poll for client disconnect while computation runs in thread pool.
+        while not compute_task.done():
+            if await request.is_disconnected():
+                print("[apply_correspondences] Client disconnected, cancelling computation")
+                cancel_event.set()
+                # Wait for the thread to finish (it will exit early on next iteration check)
+                await compute_task
+                return Response(status_code=499)
+            await asyncio.sleep(0.5)
+
+        relaxed_field, warped_image, misd_as_input = await compute_task
 
     relaxed_field_np = relaxed_field.cpu().numpy().astype(np.float32)
     warped_image_np = warped_image.cpu().numpy().astype(np.float32)
diff --git a/zetta_utils/internal b/zetta_utils/internal
index 169abd527..bb0e1032c 160000
--- a/zetta_utils/internal
+++ b/zetta_utils/internal
@@ -1 +1 @@
-Subproject commit 169abd52771d8a8a58c06d3adc30847d5d45067b
+Subproject commit bb0e1032ce81467db17d786d7fcefbeb41434cc5