diff --git a/copyparty/up2k.py b/copyparty/up2k.py
index e71936c4..561c0a78 100644
--- a/copyparty/up2k.py
+++ b/copyparty/up2k.py
@@ -16,7 +16,7 @@ import threading
 from copy import deepcopy
 
 from .__init__ import WINDOWS, PY2
-from .util import Pebkac, Queue, fsdec, fsenc, sanitize_fn, ren_open
+from .util import Pebkac, Queue, fsdec, fsenc, sanitize_fn, ren_open, atomic_move
 
 HAVE_SQLITE3 = False
 try:
@@ -423,11 +423,7 @@ class Up2k(object):
             if ret > 0:
                 return ret, src
 
-            if not PY2:
-                os.replace(src, dst)
-            else:
-                os.unlink(dst)
-                os.rename(src, dst)
+            atomic_move(src, dst)
 
             if WINDOWS:
                 self.lastmod_q.put([dst, (int(time.time()), int(job["lmod"]))])
@@ -545,14 +541,14 @@ class Up2k(object):
                     self.log("lmod", "failed to utime ({}, {})".format(path, times))
 
     def _snapshot(self):
+        persist_interval = 30  # persist unfinished uploads index every 30 sec
+        discard_interval = 3600  # drop unfinished uploads after 1 hour inactivity
         prev = {}
         while True:
-            # persist pending uploads every 60sec
-            time.sleep(30)
+            time.sleep(persist_interval)
             for k, reg in self.registry.items():
                 now = time.time()
-                # discard abandoned uploads (idle >= 1h)
-                rm = [x for x in reg.values() if now - x["poke"] > 60]
+                rm = [x for x in reg.values() if now - x["poke"] > discard_interval]
                 if rm:
                     m = "dropping {} abandoned uploads in {}".format(len(rm), k)
                     vis = [self._vis_job_progress(x) for x in rm]
@@ -560,22 +556,33 @@ class Up2k(object):
                     for job in rm:
                         del reg[job["wark"]]
                         try:
-                            # try to remove the placeholder zero-byte file too
+                            # remove the placeholder zero-byte file (keep the PARTIAL)
                             path = os.path.join(job["ptop"], job["prel"], job["name"])
                             if os.path.getsize(path) == 0:
                                 os.unlink(path)
                         except:
                             pass
 
-                newest = max(x["poke"] for _, x in reg.items()) if reg else 0
-                etag = [len(reg), newest]
-                if etag == prev.get(k, None) or not reg:
+                path = os.path.join(k, ".hist", "up2k.snap")
+                if not reg:
+                    if k not in prev or prev[k] is not None:
+                        prev[k] = None
+                        if os.path.exists(path):
+                            os.unlink(path)
+
                     continue
 
+                newest = max(x["poke"] for _, x in reg.items()) if reg else 0
+                etag = [len(reg), newest]
+                if etag == prev.get(k, None):
+                    continue
+
+                path2 = "{}.{}".format(path, os.getpid())
                 j = json.dumps(reg, indent=2, sort_keys=True).encode("utf-8")
-                path = os.path.join(k, ".hist", "up2k.snap")
-                with gzip.GzipFile(path, "wb") as f:
+                with gzip.GzipFile(path2, "wb") as f:
                     f.write(j)
 
+                atomic_move(path2, path)
+
                 self.log("up2k", "snap: {} |{}|".format(path, len(reg.keys())))
                 prev[k] = etag
diff --git a/copyparty/util.py b/copyparty/util.py
index a009a1c8..45e0c50f 100644
--- a/copyparty/util.py
+++ b/copyparty/util.py
@@ -549,6 +549,16 @@ else:
     fsdec = w8dec
 
 
+def atomic_move(src, dst):
+    if not PY2:
+        os.replace(src, dst)
+    else:
+        if os.path.exists(dst):
+            os.unlink(dst)
+
+        os.rename(src, dst)
+
+
 def read_socket(sr, total_size):
     remains = total_size
     while remains > 0: