diff --git a/api/worker.go b/api/worker.go
index 1a350ddc..adf4fd4c 100644
--- a/api/worker.go
+++ b/api/worker.go
@@ -222,7 +222,7 @@ func (w *Worker) GetTransaction(txid string, spendingTxs bool) (*Tx, error) {
 
 func (w *Worker) getAddressTxids(addrDesc bchain.AddressDescriptor, mempool bool) ([]string, error) {
 	var err error
-	txids := make([]string, 0)
+	txids := make([]string, 0, 4)
 	if !mempool {
 		err = w.db.GetAddrDescTransactions(addrDesc, 0, ^uint32(0), func(txid string, vout uint32, isOutput bool) error {
 			txids = append(txids, txid)
@@ -484,7 +484,7 @@ func (w *Worker) GetAddressUtxo(address string) ([]AddressUtxo, error) {
 	if err != nil {
 		return nil, NewAPIError(fmt.Sprintf("Invalid address, %v", err), true)
 	}
-	var r []AddressUtxo
+	r := make([]AddressUtxo, 0, 8)
 	// get utxo from mempool
 	txm, err := w.getAddressTxids(addrDesc, true)
 	if err != nil {
@@ -516,16 +516,17 @@ func (w *Worker) GetAddressUtxo(address string) ([]AddressUtxo, error) {
 	if err != nil {
 		return nil, NewAPIError(fmt.Sprintf("Address not found, %v", err), true)
 	}
+	var checksum big.Int
 	// ba can be nil if the address is only in mempool!
 	if ba != nil && ba.BalanceSat.Uint64() > 0 {
 		type outpoint struct {
 			txid string
 			vout uint32
 		}
-		txids := make([]outpoint, 0)
+		outpoints := make([]outpoint, 0, 8)
 		err = w.db.GetAddrDescTransactions(addrDesc, 0, ^uint32(0), func(txid string, vout uint32, isOutput bool) error {
 			if isOutput {
-				txids = append(txids, outpoint{txid, vout})
+				outpoints = append(outpoints, outpoint{txid, vout})
 			}
 			return nil
 		})
@@ -534,14 +535,14 @@ func (w *Worker) GetAddressUtxo(address string) ([]AddressUtxo, error) {
 		}
 		var lastTxid string
 		var ta *db.TxAddresses
-		total := ba.BalanceSat
+		checksum = ba.BalanceSat
 		b, _, err := w.db.GetBestBlock()
 		if err != nil {
 			return nil, err
 		}
 		bestheight := int(b)
-		for i := len(txids) - 1; i >= 0 && total.Int64() > 0; i-- {
-			o := txids[i]
+		for i := len(outpoints) - 1; i >= 0 && checksum.Int64() > 0; i-- {
+			o := outpoints[i]
 			if lastTxid != o.txid {
 				ta, err = w.db.GetTxAddresses(o.txid)
 				if err != nil {
@@ -555,20 +556,25 @@ func (w *Worker) GetAddressUtxo(address string) ([]AddressUtxo, error) {
 				if len(ta.Outputs) <= int(o.vout) {
 					glog.Warning("DB inconsistency:  txAddresses ", o.txid, " does not have enough outputs")
 				} else {
-					v := ta.Outputs[o.vout].ValueSat
-					r = append(r, AddressUtxo{
-						Txid:          o.txid,
-						Vout:          o.vout,
-						AmountSat:     v,
-						Amount:        w.chainParser.AmountToDecimalString(&v),
-						Height:        int(ta.Height),
-						Confirmations: bestheight - int(ta.Height) + 1,
-					})
-					total.Sub(&total, &v)
+					if !ta.Outputs[o.vout].Spent {
+						v := ta.Outputs[o.vout].ValueSat
+						r = append(r, AddressUtxo{
+							Txid:          o.txid,
+							Vout:          o.vout,
+							AmountSat:     v,
+							Amount:        w.chainParser.AmountToDecimalString(&v),
+							Height:        int(ta.Height),
+							Confirmations: bestheight - int(ta.Height) + 1,
+						})
+						checksum.Sub(&checksum, &v)
+					}
 				}
 			}
 		}
 	}
+	if checksum.Uint64() != 0 {
+		glog.Warning("DB inconsistency:  ", address, ": checksum is not zero")
+	}
 	glog.Info("GetAddressUtxo ", address, ", ", len(r), " utxos, finished in ", time.Since(start))
 	return r, nil
 }
diff --git a/db/rocksdb.go b/db/rocksdb.go
index e4e163f5..dcd8044c 100644
--- a/db/rocksdb.go
+++ b/db/rocksdb.go
@@ -637,7 +637,7 @@ func (d *RocksDB) getBlockTxs(height uint32) ([]blockTxs, error) {
 	}
 	defer val.Free()
 	buf := val.Data()
-	bt := make([]blockTxs, 0)
+	bt := make([]blockTxs, 0, 8)
 	for i := 0; i < len(buf); {
 		if len(buf)-i < pl {
 			glog.Error("rocksdb: Inconsistent data in blockTxs ", hex.EncodeToString(buf))
@@ -796,7 +796,7 @@ func unpackTxOutput(to *TxOutput, buf []byte) int {
 }
 
 func (d *RocksDB) packOutpoints(outpoints []outpoint) []byte {
-	buf := make([]byte, 0)
+	buf := make([]byte, 0, 32)
 	bvout := make([]byte, vlq.MaxLen32)
 	for _, o := range outpoints {
 		l := packVarint32(o.index, bvout)
@@ -808,7 +808,7 @@ func (d *RocksDB) packOutpoints(outpoints []outpoint) []byte {
 
 func (d *RocksDB) unpackOutpoints(buf []byte) ([]outpoint, error) {
 	txidUnpackedLen := d.chainParser.PackedTxidLen()
-	outpoints := make([]outpoint, 0)
+	outpoints := make([]outpoint, 0, 8)
 	for i := 0; i < len(buf); {
 		btxID := append([]byte(nil), buf[i:i+txidUnpackedLen]...)
 		i += txidUnpackedLen
diff --git a/server/socketio.go b/server/socketio.go
index 2cdd1361..9c7632d3 100644
--- a/server/socketio.go
+++ b/server/socketio.go
@@ -210,7 +210,7 @@ type resultAddressTxids struct {
 }
 
 func (s *SocketIoServer) getAddressTxids(addr []string, opts *addrOpts) (res resultAddressTxids, err error) {
-	txids := make([]string, 0)
+	txids := make([]string, 0, 8)
 	lower, higher := uint32(opts.End), uint32(opts.Start)
 	for _, address := range addr {
 		if !opts.QueryMempoolOnly {
@@ -381,7 +381,7 @@ func (s *SocketIoServer) getAddressHistory(addr []string, opts *addrOpts) (res r
 	}
 	txids := txr.Result
 	res.Result.TotalCount = len(txids)
-	res.Result.Items = make([]addressHistoryItem, 0)
+	res.Result.Items = make([]addressHistoryItem, 0, 8)
 	to := len(txids)
 	if to > opts.To {
 		to = opts.To