diff --git a/darshan-util/pydarshan/darshan/backend/cffi_backend.py b/darshan-util/pydarshan/darshan/backend/cffi_backend.py
index 22faa3407..310000b39 100644
--- a/darshan-util/pydarshan/darshan/backend/cffi_backend.py
+++ b/darshan-util/pydarshan/darshan/backend/cffi_backend.py
@@ -559,35 +559,16 @@ def log_get_dxt_record(log, mod_name, reads=True, writes=True, dtype='dict'):
     rec['write_count'] = wcnt
     rec['read_count'] = rcnt
  
-    rec['write_segments'] = []
-    rec['read_segments'] = []
-
-
     size_of = ffi.sizeof("struct dxt_file_record")
     segments = ffi.cast("struct segment_info *", buf[0] + size_of  )
-
-
-    for i in range(wcnt):
-        seg = {
-            "offset": segments[i].offset,
-            "length": segments[i].length,
-            "start_time": segments[i].start_time,
-            "end_time": segments[i].end_time
-        }
-        rec['write_segments'].append(seg)
-
-
-    for i in range(rcnt):
-        i = i + wcnt
-        seg = {
-            "offset": segments[i].offset,
-            "length": segments[i].length,
-            "start_time": segments[i].start_time,
-            "end_time": segments[i].end_time
-        }
-        rec['read_segments'].append(seg)
-
-
+    segments_buf = ffi.buffer(segments, (rcnt + wcnt) * 64 * 4)
+    segment_arr = np.frombuffer(buffer=segments_buf,
+                                dtype=[("offset", int),
+                                       ("length", int),
+                                       ("start_time", float),
+                                       ("end_time", float)])
+    rec['write_segments'] = segment_arr[:wcnt]
+    rec['read_segments'] = segment_arr[wcnt: rcnt + wcnt]
     if dtype == "pandas":
         rec['read_segments'] = pd.DataFrame(rec['read_segments'])
         rec['write_segments'] = pd.DataFrame(rec['write_segments'])
diff --git a/darshan-util/pydarshan/darshan/experimental/plots/heatmap_handling.py b/darshan-util/pydarshan/darshan/experimental/plots/heatmap_handling.py
index 08c49c599..09674a108 100644
--- a/darshan-util/pydarshan/darshan/experimental/plots/heatmap_handling.py
+++ b/darshan-util/pydarshan/darshan/experimental/plots/heatmap_handling.py
@@ -132,6 +132,10 @@ def get_rd_wr_dfs(
             # ignore for the same reason as above
             seg_df = _dict[seg_key]  # type: ignore
             if seg_df.size:
+                seg_df.columns = ["offset",
+                                  "length",
+                                  "start_time",
+                                  "end_time"]
                 # drop unused columns from the dataframe
                 seg_df = seg_df.drop(columns=drop_columns)
                 # create new column for the ranks
diff --git a/darshan-util/pydarshan/darshan/tests/test_moddxt.py b/darshan-util/pydarshan/darshan/tests/test_moddxt.py
index 5352aca4d..1cdd7bd80 100644
--- a/darshan-util/pydarshan/darshan/tests/test_moddxt.py
+++ b/darshan-util/pydarshan/darshan/tests/test_moddxt.py
@@ -1,6 +1,8 @@
 import os
 
 import pytest
+import numpy as np
+from numpy.testing import assert_allclose
 import darshan.backend.cffi_backend as backend
 from darshan.log_utils import get_log_path
 
@@ -16,24 +18,52 @@
                    'hostname': 'sn176.localdomain',
                    'write_count': 1,
                    'read_count': 0,
-                   'write_segments': [{'offset': 0,
-                                       'length': 40,
-                                       'start_time': 0.10337884305045009,
-                                       'end_time': 0.10338771319948137}],
-                   'read_segments': []}),
+                   'write_segments': np.array([(0,
+                                               40,
+                                               0.10337884305045009,
+                                               0.10338771319948137)],
+                                               dtype=[("offset", int),
+                                                      ("length", int),
+                                                      ("start_time", float),
+                                                      ("end_time", float)]),
+                   'read_segments': np.array([],
+                                             dtype=[("offset", int),
+                                                    ("length", int),
+                                                    ("start_time", float),
+                                                    ("end_time", float)])}),
     ('DXT_MPIIO', {'id': 9457796068806373448,
                    'rank': 0,
                    'hostname': 'sn176.localdomain',
                    'write_count': 1,
                    'read_count': 0,
-                   'write_segments': [{'offset': 0, 
-                                       'length': 4000,
-                                       'start_time': 0.10368914622813463,
-                                       'end_time': 0.1053433942142874}], 
-                   'read_segments': []})])
+                   'write_segments': np.array([(0,
+                                               4000,
+                                               0.10368914622813463,
+                                               0.1053433942142874)],
+                                               dtype=[("offset", int),
+                                                      ("length", int),
+                                                      ("start_time", float),
+                                                      ("end_time", float)]),
+                   'read_segments': np.array([],
+                                             dtype=[("offset", int),
+                                                    ("length", int),
+                                                    ("start_time", float),
+                                                    ("end_time", float)])})])
 def test_dxt_records(logfile, mod, expected_dict):
-    # regression guard for DXT records values
+    # regression guard for DXT records values;
+    # write_segments and read_segments are now NumPy
+    # recarrays, to save considerable memory
+    # per gh-779
     logfile = get_log_path(logfile)
     log = backend.log_open(logfile)
     rec = backend.log_get_record(log, mod)
-    assert rec == expected_dict
+    for key in expected_dict.keys():
+        if "segments" in key:
+            # careful, can't use assert_allclose directly
+            # on recarrays
+            assert_allclose(rec[key]["offset"], expected_dict[key]["offset"])
+            assert_allclose(rec[key]["length"], expected_dict[key]["length"])
+            assert_allclose(rec[key]["start_time"], expected_dict[key]["start_time"])
+            assert_allclose(rec[key]["end_time"], expected_dict[key]["end_time"])
+        else:
+            assert rec[key] == expected_dict[key]