diff --git a/src/datastruct/dict/dict.go b/src/datastruct/dict/dict.go
index eef2463..ccd6c65 100644
--- a/src/datastruct/dict/dict.go
+++ b/src/datastruct/dict/dict.go
@@ -7,66 +7,30 @@ import (
 )
 
 type Dict struct {
-    table       atomic.Value // []*Shard
-    nextTable   []*Shard
-    nextTableMu sync.Mutex
+    table       []*Shard
     count       int32
-
-    // -1: no rehashing in progress
-    // >=0 && < tableSize: table[rehashIndex] is rehashing
-    // >= tableSize: rehashing progress is finishing
-    rehashIndex int32
 }
 
 type Shard struct {
-    head  *Node
+    m  map[string]interface{}
     mutex sync.RWMutex
 }
 
-type Node struct {
-    key      string
-    val      interface{}
-    next     *Node
-    hashCode uint32
-}
 
-
-const (
-    maxCapacity      = 1 << 15
-    minCapacity      = 16
-    rehashConcurrent = 4
-    loadFactor       = 0.75
-)
-
-// return the mini 2^n  which is not less than cap
-func computeCapacity(param int) (size int) {
-    if param <= minCapacity {
-        return minCapacity
+func Make(shardCount int) *Dict {
+    if shardCount < 1 {
+        shardCount = 16
     }
-    n := param - 1
-    n |= n >> 1
-    n |= n >> 2
-    n |= n >> 4
-    n |= n >> 8
-    n |= n >> 16
-    if n < 0 || n >= maxCapacity {
-        return maxCapacity
-    } else {
-        return int(n + 1)
-    }
-}
-
-func Make(shardCountHint int) *Dict {
-    shardCount := computeCapacity(shardCountHint)
     table := make([]*Shard, shardCount)
     for i := 0; i < shardCount; i++ {
-        table[i] = &Shard{}
+        table[i] = &Shard{
+            m: make(map[string]interface{}),
+        }
     }
     d := &Dict{
         count:       0,
-        rehashIndex: -1,
+        table:   table,
     }
-    d.table.Store(table)
     return d
 }
 
@@ -85,8 +49,7 @@ func (dict *Dict) spread(hashCode uint32) uint32 {
     if dict == nil {
         panic("dict is nil")
     }
-    table, _ := dict.table.Load().([]*Shard)
-    tableSize := uint32(len(table))
+    tableSize := uint32(len(dict.table))
     return (tableSize - 1) & uint32(hashCode)
 }
 
@@ -94,74 +57,7 @@ func (dict *Dict) getShard(index uint32) *Shard {
     if dict == nil {
         panic("dict is nil")
     }
-    table, ok := dict.table.Load().([]*Shard)
-    if !ok {
-        panic("load table failed")
-    }
-    return table[index]
-}
-
-func (dict *Dict) getNextShard(hashCode uint32) *Shard {
-    if dict == nil {
-        panic("dict is nil")
-    }
-
-    // in case next table has been released during get shard
-    dict.nextTableMu.Lock()
-    defer dict.nextTableMu.Unlock()
-
-    // rehashing may be in progress or rehashing has finished while waiting nextTableMu
-    if dict.nextTable == nil {
-        return nil
-    }
-    nextTableSize := uint32(len(dict.nextTable))
-    index := (nextTableSize - 1) & uint32(hashCode)
-    return dict.nextTable[index]
-}
-
-func (dict *Dict) ensureNextTable() {
-    if dict.nextTable == nil {
-        dict.nextTableMu.Lock()
-
-        // check-lock-check
-        if dict.nextTable == nil {
-            table, _ := dict.table.Load().([]*Shard)
-            tableSize := uint32(len(table))
-            // init next table
-            nextShardCount := tableSize * 2
-            if nextShardCount > maxCapacity || nextShardCount < 0 {
-                nextShardCount = maxCapacity
-            }
-            if nextShardCount <= tableSize {
-                // reach limit, cannot resize
-                atomic.StoreInt32(&dict.rehashIndex, -1)
-                return
-            }
-            nextTable := make([]*Shard, nextShardCount)
-            var i uint32
-            for i = 0; i < nextShardCount; i++ {
-                nextTable[i] = &Shard{}
-            }
-            dict.nextTable = nextTable
-        }
-
-        dict.nextTableMu.Unlock()
-    }
-}
-
-func (shard *Shard) Get(key string) (val interface{}, exists bool) {
-    if shard == nil {
-        panic("shard is nil")
-    }
-
-    node := shard.head
-    for node != nil {
-        if node.key == key {
-            return node.val, true
-        }
-        node = node.next
-    }
-    return nil, false
+    return dict.table[index]
 }
 
 func (dict *Dict) Get(key string) (val interface{}, exists bool) {
@@ -172,34 +68,8 @@ func (dict *Dict) Get(key string) (val interface{}, exists bool) {
     index := dict.spread(hashCode)
     shard := dict.getShard(index)
     shard.mutex.RLock()
-
-    rehashIndex := atomic.LoadInt32(&dict.rehashIndex)
-    if rehashIndex >= int32(index) {
-        /*
-         * if rehashIndex > index. then the shard has finished resize, put in next table
-         * if rehashIndex == index, the shard may be resizing or just finished.
-         * Resizing will not be finished until the lock has been released
-         */
-        shard.mutex.RUnlock()
-        nextShard := dict.getNextShard(hashCode)
-        if nextShard == nil {
-            shard := dict.getShard(dict.spread(hashCode))
-            shard.mutex.RLock()
-            val, exists =  shard.Get(key)
-            shard.mutex.RUnlock()
-        } else {
-            nextShard.mutex.RLock()
-            val, exists = nextShard.Get(key)
-            nextShard.mutex.RUnlock()
-        }
-    } else {
-        /*
-         * if rehashing not in progress or the shard has not been rehashing, put in current shard
-         */
-        val, exists =  shard.Get(key)
-        shard.mutex.RUnlock()
-    }
-
+    defer shard.mutex.RUnlock()
+    val, exists = shard.m[key]
     return
 }
 
@@ -210,42 +80,6 @@ func (dict *Dict) Len() int {
     return int(atomic.LoadInt32(&dict.count))
 }
 
-func (shard *Shard) Put(key string, val interface{}, hashCode uint32) int {
-    if shard == nil {
-        panic("shard is nil")
-    }
-
-    node := shard.head
-    if node == nil {
-        // empty shard
-        node = &Node{
-            key:      key,
-            val:      val,
-            hashCode: hashCode,
-        }
-        shard.head = node
-        return 1
-    } else {
-        for {
-            if node.key == key {
-                // existed node
-                node.val = val
-                return 0
-            }
-            if node.next == nil {
-                // append
-                node.next = &Node{
-                    key:      key,
-                    val:      val,
-                    hashCode: hashCode,
-                }
-                return 1
-            }
-            node = node.next
-        }
-    }
-}
-
 // return the number of new inserted key-value
 func (dict *Dict) Put(key string, val interface{}) (result int) {
     if dict == nil {
@@ -255,66 +89,15 @@ func (dict *Dict) Put(key string, val interface{}) (result int) {
     index := dict.spread(hashCode)
     shard := dict.getShard(index)
     shard.mutex.Lock()
+    defer shard.mutex.Unlock()
 
-    rehashIndex := atomic.LoadInt32(&dict.rehashIndex)
-    if rehashIndex >= int32(index) {
-        /* if rehashIndex > index. then the shard has finished resize, put in next table
-         * if rehashIndex == index, the shard may be resizing or just finished.
-         * Resizing will not be finished until the lock has been released
-         */
-        shard.mutex.Unlock()
-        nextShard := dict.getNextShard(hashCode)
-        if nextShard == nil {
-            shard := dict.getShard(dict.spread(hashCode))
-            shard.mutex.Lock()
-            result = shard.Put(key, val, hashCode)
-            shard.mutex.Unlock()
-        } else {
-            nextShard.mutex.Lock()
-            result = nextShard.Put(key, val, hashCode)
-            nextShard.mutex.Unlock()
-        }
+    if _, ok := shard.m[key]; ok {
+        shard.m[key] = val
+        return 0
     } else {
-        /*
-         * if rehashing not in progress or the shard has not been rehashing, put in current shard
-         */
-        result = shard.Put(key, val, hashCode)
-        shard.mutex.Unlock()
-    }
-    if result == 1 {
+        shard.m[key] = val
         dict.addCount()
-    }
-    return result
-}
-
-func (shard *Shard) PutIfAbsent(key string, val interface{}, hashCode uint32)int {
-    node := shard.head
-    if node == nil {
-        // empty shard
-        node = &Node{
-            key:      key,
-            val:      val,
-            hashCode: hashCode,
-        }
-        shard.head = node
         return 1
-    } else {
-        for {
-            if node.key == key {
-                // existed node
-                return 0
-            }
-            if node.next == nil {
-                // append
-                node.next = &Node{
-                    key:      key,
-                    val:      val,
-                    hashCode: hashCode,
-                }
-                return 1
-            }
-            node = node.next
-        }
     }
 }
 
@@ -327,45 +110,17 @@ func (dict *Dict) PutIfAbsent(key string, val interface{}) (result int) {
     index := dict.spread(hashCode)
     shard := dict.getShard(index)
     shard.mutex.Lock()
-    rehashIndex := atomic.LoadInt32(&dict.rehashIndex)
-    if rehashIndex >= int32(index) {
-        shard.mutex.Unlock()
-        nextShard := dict.getNextShard(hashCode)
-        if nextShard == nil {
-            shard := dict.getShard(dict.spread(hashCode))
-            shard.mutex.Lock()
-            result = shard.PutIfAbsent(key, val, hashCode)
-            shard.mutex.Unlock()
-        } else {
-            nextShard.mutex.Lock()
-            result = nextShard.PutIfAbsent(key, val, hashCode)
-            nextShard.mutex.Unlock()
-        }
+    defer shard.mutex.Unlock()
+
+    if _, ok := shard.m[key]; ok {
+        return 0
     } else {
-        result = shard.PutIfAbsent(key, val, hashCode)
-        shard.mutex.Unlock()
-    }
-    if result == 1 {
+        shard.m[key] = val
         dict.addCount()
+        return 1
     }
-    return result
 }
 
-func (shard *Shard) PutIfExists(key string, val interface{})int {
-    if shard == nil {
-        panic("shard is nil")
-    }
-
-    node := shard.head
-    for node != nil {
-        if node.key == key {
-            node.val = val
-            return 1
-        }
-        node = node.next
-    }
-    return 0
-}
 
 // return the number of updated key-value
 func (dict *Dict) PutIfExists(key string, val interface{})(result int) {
@@ -376,53 +131,14 @@ func (dict *Dict) PutIfExists(key string, val interface{})(result int) {
     index := dict.spread(hashCode)
     shard := dict.getShard(index)
     shard.mutex.Lock()
-    rehashIndex := atomic.LoadInt32(&dict.rehashIndex)
-    if rehashIndex >= int32(index) {
-        shard.mutex.Unlock()
-        nextShard := dict.getNextShard(hashCode)
-        if nextShard == nil {
-            shard := dict.getShard(dict.spread(hashCode))
-            shard.mutex.Lock()
-            result = shard.PutIfExists(key, val)
-            shard.mutex.Unlock()
-        } else {
-            nextShard.mutex.Lock()
-            result = nextShard.PutIfExists(key, val)
-            nextShard.mutex.Unlock()
-        }
-    } else {
-        result = shard.PutIfExists(key, val)
-        shard.mutex.Unlock()
-    }
-    return
-}
+    defer shard.mutex.Unlock()
 
-func (shard *Shard) Remove(key string) int {
-    if shard == nil {
-        panic("shard is nil")
-    }
-
-    node := shard.head
-    if node == nil {
-        // empty shard
-        return 0
-    } else if node.key == key {
-        // remove first node
-        shard.head = node.next
+    if _, ok := shard.m[key]; ok {
+        shard.m[key] = val
         return 1
     } else {
-        prev := node
-        node = node.next
-        for node != nil {
-            if node.key == key {
-                prev.next = node.next
-                return 1
-            }
-            prev = node
-            node = node.next
-        }
+        return 0
     }
-    return 0
 }
 
 // return the number of deleted key-value
@@ -434,144 +150,23 @@ func (dict *Dict) Remove(key string)(result int) {
     index := dict.spread(hashCode)
     shard := dict.getShard(index)
     shard.mutex.Lock()
+    defer shard.mutex.Unlock()
 
-    rehashIndex := atomic.LoadInt32(&dict.rehashIndex)
-    if rehashIndex >= int32(index) {
-        shard.mutex.Unlock()
-        nextShard := dict.getNextShard(hashCode)
-        if nextShard == nil {
-            shard := dict.getShard(dict.spread(hashCode))
-            shard.mutex.Lock()
-            result = shard.Remove(key)
-            shard.mutex.Unlock()
-        } else {
-            nextShard.mutex.Lock()
-            result = nextShard.Remove(key)
-            nextShard.mutex.Unlock()
-        }
+    if _, ok := shard.m[key]; ok {
+        delete(shard.m, key)
+        return 1
     } else {
-        shard := dict.getShard(dict.spread(hashCode))
-        result = shard.Remove(key)
-        shard.mutex.Unlock()
-    }
-    if result > 0 {
-        atomic.AddInt32(&dict.count, -1)
+        return 0
     }
     return
 }
 
 func (dict *Dict) addCount() int32 {
-    count := atomic.AddInt32(&dict.count, 1)
-    table, _ := dict.table.Load().([]*Shard)
-    if float64(count) >= float64(len(table))*loadFactor {
-       dict.resize()
-    }
-    return count
-}
-
-func (dict *Dict) resize() {
-    if !atomic.CompareAndSwapInt32(&dict.rehashIndex, -1, 0) {
-        // resize already in progress
-        return
-    }
-    dict.ensureNextTable()
-
-    var wg sync.WaitGroup
-    wg.Add(rehashConcurrent)
-    for i := 0; i < rehashConcurrent; i++ {
-        go dict.transfer(&wg)
-    }
-    wg.Wait()
-
-    // finish rehash
-    dict.nextTableMu.Lock()
-    dict.table.Store(dict.nextTable)
-    dict.nextTable = nil
-    atomic.StoreInt32(&dict.rehashIndex, -1)
-    dict.nextTableMu.Unlock()
-}
-
-func (dict *Dict) transfer(wg *sync.WaitGroup) {
-    table, _ := dict.table.Load().([]*Shard)
-    tableSize := uint32(len(table))
-    // dict.rehashIndex must >= 0
-    for {
-        i := uint32(atomic.AddInt32(&dict.rehashIndex, 1)) - 1
-        if i >= tableSize {
-            wg.Done()
-            return
-        }
-        shard := dict.getShard(i)
-        shard.mutex.RLock()
-
-        nextShard0 := dict.nextTable[i]
-        nextShard1 := dict.nextTable[i+tableSize]
-
-        nextShard0.mutex.RLock()
-        nextShard1.mutex.RLock()
-
-        var head0, head1 *Node
-        var tail0, tail1 *Node
-        node := shard.head
-        for node != nil {
-            // split current shard to 2 shards in next table
-            if node.hashCode&tableSize == 0 {
-                if head0 == nil {
-                    head0 = node
-                } else {
-                    tail0.next = node
-                }
-                tail0 = node
-            } else {
-                if head1 == nil {
-                    head1 = node
-                } else {
-                    tail1.next = node
-                }
-                tail1 = node
-            }
-            node = node.next
-        }
-
-        if tail0 != nil {
-            tail0.next = nil
-
-            nextShard0.head = head0
-        }
-
-        if tail1 != nil {
-            tail1.next = nil
-
-            nextShard1.head = head1
-        }
-
-        nextShard1.mutex.RUnlock()
-        nextShard0.mutex.RUnlock()
-        shard.mutex.RUnlock()
-    }
+    return atomic.AddInt32(&dict.count, 1)
 }
 
 type Consumer func(key string, val interface{})bool
 
-func (shard *Shard) ForEach(consumer Consumer)bool {
-    if shard == nil {
-        panic("shard is nil")
-    }
-    shard.mutex.RLock()
-    defer shard.mutex.RUnlock()
-
-    node := shard.head
-    for node != nil {
-        toContinue := consumer(node.key, node.val)
-        if !toContinue {
-            return false
-        }
-        node = node.next
-    }
-    return true
-}
-
-
 /*
  * may not contains new entry inserted during traversal
  */
@@ -579,43 +174,14 @@ func (dict *Dict)ForEach(consumer Consumer) {
    if dict == nil {
        panic("dict is nil")
    }
-   table, ok := dict.table.Load().([]*Shard)
-   if !ok {
-       panic("load table failed")
-   }
 
-   var rehashIndex int32
-   tableSize := len(table)
-   for index, shard := range table {
-       rehashIndex = atomic.LoadInt32(&dict.rehashIndex)
-       if rehashIndex >= int32(index) {
-           // current slot has rehashed
-           if dict.nextTable == nil {
-               // rehash has finished, traver current table
-               // local variable `table` will not change to nextTable
-               if !shard.ForEach(consumer) {
-                   break
-               }
-           }
-
-           i0 := index
-           nextShard0 := dict.nextTable[i0]
-           if nextShard0 != nil {
-               if !nextShard0.ForEach(consumer) {
-                   break
-               }
-           }
-
-           i1 := index + tableSize
-           nextShard1 := dict.nextTable[i1]
-           if nextShard1 != nil {
-               if !nextShard1.ForEach(consumer) {
-                   break
-               }
-           }
-       } else {
-           if !shard.ForEach(consumer) {
-               break
+   for _, shard := range dict.table {
+       for key, value := range shard.m {
+           shard.mutex.RLock()
+           continues := consumer(key, value)
+           shard.mutex.RUnlock()
+           if !continues {
+               return
            }
        }
    }
@@ -643,21 +209,10 @@ func (shard *Shard)RandomKey()string {
     shard.mutex.RLock()
     defer shard.mutex.RUnlock()
 
-    keys := make([]string, 0)
-    i := 0
-    node := shard.head
-    for node != nil {
-        if node.key != "" {
-            keys = append(keys, node.key)
-            i++
-        }
-        node = node.next
-    }
-    if i > 0 {
-        return keys[rand.Intn(i)]
-    } else {
-        return ""
+    for key := range shard.m {
+        return key
     }
+    return ""
 }
 
 func (dict *Dict)RandomKeys(limit int)[]string {
@@ -665,8 +220,7 @@ func (dict *Dict)RandomKeys(limit int)[]string {
     if limit >= size {
         return dict.Keys()
     }
-    table, _ := dict.table.Load().([]*Shard)
-    shardCount := len(table)
+    shardCount := len(dict.table)
 
     result := make([]string, limit)
     for i := 0; i < limit; {
@@ -689,8 +243,7 @@ func (dict *Dict)RandomDistinctKeys(limit int)[]string {
         return dict.Keys()
     }
 
-    table, _ := dict.table.Load().([]*Shard)
-    shardCount := len(table)
+    shardCount := len(dict.table)
     result := make(map[string]bool)
     for len(result) < limit {
         shardIndex := uint32(rand.Intn(shardCount))
diff --git a/src/datastruct/lock/lock_map.go b/src/datastruct/lock/lock_map.go
index 09100fc..f927dda 100644
--- a/src/datastruct/lock/lock_map.go
+++ b/src/datastruct/lock/lock_map.go
@@ -67,7 +67,6 @@ func (locks *Locks)UnLock(key string) {
 func (locks *Locks)RUnLock(key string) {
     index := locks.spread(fnv32(key))
     mu := locks.table[index]
-    mu.Lock()
     mu.RUnlock()
 }
 
diff --git a/src/db/db.go b/src/db/db.go
index 5a011d9..07510e7 100644
--- a/src/db/db.go
+++ b/src/db/db.go
@@ -46,12 +46,12 @@ var router = MakeRouter()
 
 func MakeDB() *DB {
     db := &DB{
-        Data:     dict.Make(1024),
-        TTLMap:   dict.Make(128),
+        Data:     dict.Make(128),
+        TTLMap:   dict.Make(64),
         Locker:   lock.Make(128),
         interval: 5 * time.Second,
 
-        subs:     dict.Make(16),
+        subs:     dict.Make(4),
         subsLocker: lock.Make(16),
     }
     db.TimerTask()
diff --git a/src/db/hash.go b/src/db/hash.go
index 32af90a..031d080 100644
--- a/src/db/hash.go
+++ b/src/db/hash.go
@@ -27,7 +27,7 @@ func (db *DB) getOrInitDict(key string)(dict *Dict.Dict, inited bool, errReply r
     }
     inited = false
     if dict == nil {
-        dict = Dict.Make(0)
+        dict = Dict.Make(1)
         db.Data.Put(key, &DataEntity{
             Data: dict,
         })