diff --git a/plotly/figure_factory/_scatterplot.py b/plotly/figure_factory/_scatterplot.py
index 75895272615..271a35993dd 100644
--- a/plotly/figure_factory/_scatterplot.py
+++ b/plotly/figure_factory/_scatterplot.py
@@ -25,14 +25,15 @@ def endpts_to_intervals(endpts):
     """
     length = len(endpts)
     # Check if endpts is a list or tuple
-    if not (isinstance(endpts, (tuple)) or isinstance(endpts, (list))):
+    if not isinstance(endpts, (list, tuple)):
         raise exceptions.PlotlyError(
             "The intervals_endpts argument must "
             "be a list or tuple of a sequence "
             "of increasing numbers."
         )
-    # Check if endpts contains only numbers
-    for item in endpts:
+    # Single-pass validation for both string element and increasing check
+    prev = None
+    for i, item in enumerate(endpts):
         if isinstance(item, str):
             raise exceptions.PlotlyError(
                 "The intervals_endpts argument "
@@ -40,27 +41,20 @@ def endpts_to_intervals(endpts):
                 "sequence of increasing "
                 "numbers."
             )
-    # Check if numbers in endpts are increasing
-    for k in range(length - 1):
-        if endpts[k] >= endpts[k + 1]:
+        if prev is not None and prev >= item:
             raise exceptions.PlotlyError(
                 "The intervals_endpts argument "
                 "must be a list or tuple of a "
                 "sequence of increasing "
                 "numbers."
             )
-    else:
-        intervals = []
-        # add -inf to intervals
-        intervals.append([float("-inf"), endpts[0]])
-        for k in range(length - 1):
-            interval = []
-            interval.append(endpts[k])
-            interval.append(endpts[k + 1])
-            intervals.append(interval)
-        # add +inf to intervals
-        intervals.append([endpts[length - 1], float("inf")])
-        return intervals
+        prev = item
+
+    # Build the intervals efficiently using list comprehensions
+    intervals = [[float("-inf"), endpts[0]]]
+    intervals.extend([[endpts[k], endpts[k + 1]] for k in range(length - 1)])
+    intervals.append([endpts[-1], float("inf")])
+    return intervals
 
 
 def hide_tick_labels_from_box_subplots(fig):