diff --git a/rocksdb/main.cpp b/rocksdb/main.cpp
index 0ab578b..fa160d1 100644
--- a/rocksdb/main.cpp
+++ b/rocksdb/main.cpp
@@ -23,6 +23,11 @@
 #include "CLI/CLI.hpp"
 #include "instant.h"
 
+template<class T>
+static void black_box(const T &t) {
+    asm volatile("" ::"m"(t) : "memory");
+}
+
 struct Args {
     size_t threads;
     size_t iterations;
@@ -131,7 +136,7 @@ int main(int argc, char *argv[]) {
             tmp.resize(args.key_size, 'x');
             key.emplace_back(std::move(tmp));
         }
-        if (args.mode == "get" || args.random) {
+        if (args.mode == "get" || args.random || args.mode == "scan") {
             std::shuffle(keys.begin(), keys.end(), gen);
         }
         keys.emplace_back(std::move(key));
@@ -150,12 +155,14 @@ int main(int argc, char *argv[]) {
         }
         kv->Commit();
         delete kv;
-        delete handle;
-        delete db;
-        handles.clear();
-        // re-open db
-        s = rocksdb::OptimisticTransactionDB::Open(options, args.path, cfd, &handles, &db);
-        assert(s.ok());
+        if (args.mode == "get") {
+            delete handle;
+            delete db;
+            handles.clear();
+            // re-open db
+            s = rocksdb::OptimisticTransactionDB::Open(options, args.path, cfd, &handles, &db);
+            assert(s.ok());
+        }
     }
 
     handle = handles[0];
@@ -203,6 +210,8 @@ int main(int argc, char *argv[]) {
                 auto *iter = db->NewIterator(ropt);
                 iter->Seek(prefix);
                 while (iter->Valid()) {
+                    black_box(iter->key());
+                    black_box(iter->value());
                     iter->Next();
                 }
                 delete iter;
diff --git a/src/main.rs b/src/main.rs
index 8bbdfa8..b106dab 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -81,7 +81,8 @@ fn main() {
     opt.sync_on_write = false;
     opt.over_provision = true; // large value will use lots of memeory
     opt.inline_size = args.blob_size;
-    opt.tmp_store = args.mode != "get" && args.mode != "scan";
+    opt.tmp_store = args.mode != "get";
+    opt.cache_capacity = 3 << 30;
     let mut saved = opt.clone();
     saved.tmp_store = false;
     let mut db = Mace::new(opt.validate().unwrap()).unwrap();
@@ -96,7 +97,7 @@ fn main() {
             key.resize(args.key_size, b'x');
             tk.push(key);
         }
-        if args.random || args.mode == "get" {
+        if args.random || args.mode == "get" || args.mode == "scan" {
             tk.shuffle(&mut rng);
         }
         keys.push(tk);
@@ -110,10 +111,12 @@ fn main() {
             }
         });
         pre_tx.commit().unwrap();
-        drop(db);
-        // re-open db
-        saved.tmp_store = true;
-        db = Mace::new(saved.validate().unwrap()).unwrap();
+        if args.mode == "get" {
+            drop(db);
+            // re-open db
+            saved.tmp_store = true;
+            db = Mace::new(saved.validate().unwrap()).unwrap();
+        }
     }
 
     let barrier = Arc::new(std::sync::Barrier::new(args.threads));
@@ -131,6 +134,7 @@ fn main() {
             let st = start_time.clone();
             let val = value.clone();
             let prefix = format!("key_{tid}");
+            println!("prefix {}", prefix);
 
             std::thread::spawn(move || {
                 // coreid::bind_core(tid);