diff --git a/logstore.cpp b/logstore.cpp
index 51df3d9..84b1168 100644
--- a/logstore.cpp
+++ b/logstore.cpp
@@ -538,7 +538,21 @@ datatuple * logtable<TUPLE>::findTuple_first(int xid, datatuple::key_t key, size
 template<class TUPLE>
 datatuple * logtable<TUPLE>::insertTupleHelper(datatuple *tuple)
 {
-  //find the previous tuple with same key in the memtree if exists
+  bool need_free = true;
+  if(!tuple->isDelete() && expiry != 0) {
+    // XXX hack for paper experiment
+    current_timestamp++;
+    size_t ts_sz = sizeof(int64_t);
+    int64_t ts = current_timestamp;
+    int64_t kl = tuple->strippedkeylen();
+    byte * newkey = (byte*)malloc(kl + 1 + ts_sz);
+    memcpy(newkey, tuple->strippedkey(), kl);
+    newkey[kl] = 0;
+    memcpy(newkey+kl+1, &ts, ts_sz);
+    tuple = datatuple::create(newkey, kl+ 1+ ts_sz, tuple->data(), tuple->datalen());
+    free(newkey);
+    need_free = true;
+  }  //find the previous tuple with same key in the memtree if exists
   memTreeComponent<datatuple>::rbtree_t::iterator rbitr = tree_c0->find(tuple);
   datatuple * t  = 0;
   datatuple * pre_t = 0;
@@ -562,6 +576,8 @@ datatuple * logtable<TUPLE>::insertTupleHelper(datatuple *tuple)
     tree_c0->insert(t);
   }
 
+  if(need_free) { TUPLE::freetuple(tuple); }
+
   return pre_t;
 }
 template<class TUPLE>
diff --git a/merger.cpp b/merger.cpp
index d183581..c16884d 100644
--- a/merger.cpp
+++ b/merger.cpp
@@ -33,7 +33,7 @@ bool insert_filter(logtable<datatuple> * ltable, datatuple * t, bool dropDeletes
     }
   }
   if(!ltable->expiry) { return true; }
-  if(t->timestamp() > ltable->current_timestamp + ltable->expiry) { return false; }
+  if(t->timestamp() < ltable->current_timestamp - ltable->expiry) { return false; }
   return true;
 }
 
diff --git a/newserver.cpp b/newserver.cpp
index 3c32968..d86c48e 100644
--- a/newserver.cpp
+++ b/newserver.cpp
@@ -23,6 +23,7 @@ int main(int argc, char *argv[])
     signal(SIGPIPE, SIG_IGN);
     int64_t c0_size = 1024 * 1024 * 512 * 1;
     int log_mode = 0; // do not log by default.
+    int64_t expiry_delta = 0;  // do not gc by default
     stasis_buffer_manager_size = 1 * 1024 * 1024 * 1024 / PAGE_SIZE;  // 1.5GB total
 
     for(int i = 1; i < argc; i++) {
@@ -37,8 +38,11 @@ int main(int argc, char *argv[])
     	} else if(!strcmp(argv[i], "--log-mode")) {
     		i++;
     		log_mode = atoi(argv[i]);
+        } else if(!strcmp(argv[i], "--expiry-delta")) {
+            i++;
+            expiry_delta = atoi(argv[i]);
     	} else {
-    		fprintf(stderr, "Usage: %s [--test|--benchmark] [--log-mode <int>]", argv[0]);
+    		fprintf(stderr, "Usage: %s [--test|--benchmark] [--log-mode <int>] [--expiry-delta <int>]", argv[0]);
     		abort();
     	}
     }
@@ -51,6 +55,7 @@ int main(int argc, char *argv[])
       recordid table_root = ROOT_RECORD;
     {
 		logtable<datatuple> ltable(log_mode, c0_size);
+		ltable.expiry = expiry_delta;
 
 		if(TrecordType(xid, ROOT_RECORD) == INVALID_SLOT) {
 			printf("Creating empty logstore\n");