diff --git a/piker/data/flows.py b/piker/data/flows.py
index f1b8eabf..01ed7851 100644
--- a/piker/data/flows.py
+++ b/piker/data/flows.py
@@ -48,13 +48,13 @@ from ._sharedmem import (
 from ._sampling import (
     open_sample_stream,
 )
-from .._profile import (
-    Profiler,
-    pg_profile_enabled,
-)
+# from .._profile import (
+#     Profiler,
+#     pg_profile_enabled,
+# )
 
 if TYPE_CHECKING:
-    from pyqtgraph import PlotItem
+    # from pyqtgraph import PlotItem
     from .feed import Feed
 
 
@@ -222,18 +222,18 @@ class Flume(Struct):
     def get_index(
         self,
         time_s: float,
+        array: np.ndarray,
 
-    ) -> int:
+    ) -> int | float:
         '''
         Return array shm-buffer index for for epoch time.
 
         '''
-        array = self.rt_shm.array
         times = array['time']
-        mask = (times >= time_s)
-
-        if any(mask):
-            return array['index'][mask][0]
-
-        # just the latest index
-        return array['index'][-1]
+        first = np.searchsorted(
+            times,
+            time_s,
+            side='left',
+        )
+        imx = times.shape[0] - 1
+        return min(first, imx)
diff --git a/piker/ui/order_mode.py b/piker/ui/order_mode.py
index 1dd49872..ee0196f7 100644
--- a/piker/ui/order_mode.py
+++ b/piker/ui/order_mode.py
@@ -494,7 +494,7 @@ class OrderMode:
 
         uuid: str,
         price: float,
-        arrow_index: float,
+        time_s: float,
 
         pointing: Optional[str] = None,
 
@@ -513,18 +513,26 @@ class OrderMode:
         '''
         dialog = self.dialogs[uuid]
         lines = dialog.lines
+        chart = self.chart
+
         # XXX: seems to fail on certain types of races?
         # assert len(lines) == 2
         if lines:
-            flume: Flume = self.feed.flumes[self.chart.linked.symbol.fqsn]
+            flume: Flume = self.feed.flumes[chart.linked.symbol.fqsn]
             _, _, ratio = flume.get_ds_info()
-            for i, chart in [
-                (arrow_index, self.chart),
-                (flume.izero_hist
-                 +
-                 round((arrow_index - flume.izero_rt)/ratio),
-                 self.hist_chart)
+
+            for chart, shm in [
+                (self.chart, flume.rt_shm),
+                (self.hist_chart, flume.hist_shm),
             ]:
+                viz = chart.get_viz(chart.name)
+                index_field = viz.index_field
+                arr = shm.array
+                index = flume.get_index(time_s, arr)
+
+                if index_field == 'time':
+                    i = arr['time'][index]
+
                 self.arrows.add(
                     chart.plotItem,
                     uuid,
@@ -933,6 +941,8 @@ async def process_trade_msg(
     fmsg = pformat(msg)
     log.debug(f'Received order msg:\n{fmsg}')
     name = msg['name']
+    viz = mode.chart.get_viz(mode.chart.name)
+    index_field = viz.index_field
 
     if name in (
         'position',
@@ -1037,11 +1047,11 @@ async def process_trade_msg(
             # should only be one "fill" for an alert
             # add a triangle and remove the level line
             req = Order(**req)
-            index = flume.get_index(time.time())
+            tm = time.time()
             mode.on_fill(
                 oid,
                 price=req.price,
-                arrow_index=index,
+                time_s=tm,
             )
             mode.lines.remove_line(uuid=oid)
             msg.req = req
@@ -1070,6 +1080,8 @@ async def process_trade_msg(
             details = msg.brokerd_msg
 
             # TODO: put the actual exchange timestamp?
+            # TODO: some kinda progress system?
+
             # NOTE: currently the ``kraken`` openOrders sub
             # doesn't deliver their engine timestamp as part of
             # it's schema, so this value is **not** from them
@@ -1080,15 +1092,11 @@ async def process_trade_msg(
             # a true backend one? This will require finagling
             # with how each backend tracks/summarizes time
             # stamps for the downstream API.
-            index = flume.get_index(
-                details['broker_time']
-            )
-
-            # TODO: some kinda progress system
+            tm = details['broker_time']
             mode.on_fill(
                 oid,
                 price=details['price'],
-                arrow_index=index,
+                time_s=tm,
                 pointing='up' if action == 'buy' else 'down',
             )