@@ -213,7 +213,7 @@ if err := os.RemoveAll(dir); err != nil {
 			panic(err)
 		}
 	}()
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeTxSelector, 0)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128, Type: statedb.TypeTxSelector, NLevels: 0})
 	if err != nil {
 		panic(err)
 	}

@@ -2,6 +2,7 @@ package batchbuilder
 
 import (
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/db/kvdb"
 	"github.com/hermeznetwork/hermez-node/db/statedb"
 	"github.com/hermeznetwork/hermez-node/txprocessor"
 	"github.com/hermeznetwork/tracerr"
@@ -28,8 +29,14 @@
 // NewBatchBuilder constructs a new BatchBuilder, and executes the bb.Reset
 // method
 func NewBatchBuilder(dbpath string, synchronizerStateDB *statedb.StateDB, batchNum common.BatchNum, nLevels uint64) (*BatchBuilder, error) {
-	localStateDB, err := statedb.NewLocalStateDB(dbpath, 128, synchronizerStateDB,
-		statedb.TypeBatchBuilder, int(nLevels))
+	localStateDB, err := statedb.NewLocalStateDB(
+		statedb.Config{
+			Path:    dbpath,
+			Keep:    kvdb.DefaultKeep,
+			Type:    statedb.TypeBatchBuilder,
+			NLevels: int(nLevels),
+		},
+		synchronizerStateDB)
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}

@@ -15,7 +15,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.Nil(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
-	synchDB, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 0)
+	synchDB, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128, Type: statedb.TypeBatchBuilder, NLevels: 0})
 	assert.Nil(t, err)
 
 	bbDir, err := ioutil.TempDir("", "tmpBatchBuilderDB")

@@ -97,7 +97,8 @@ var err error
 	syncDBPath, err = ioutil.TempDir("", "tmpSyncDB")
 	require.NoError(t, err)
 	deleteme = append(deleteme, syncDBPath)
-	syncStateDB, err := statedb.NewStateDB(syncDBPath, 128, statedb.TypeSynchronizer, 48)
+	syncStateDB, err := statedb.NewStateDB(statedb.Config{Path: syncDBPath, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 48})
 	assert.NoError(t, err)
 
 	pass := os.Getenv("POSTGRES_PASS")

@@ -200,15 +200,17 @@ p.stats = statsVars.Stats
 				p.syncSCVars(statsVars.Vars)
 			case <-time.After(waitDuration):
 				batchNum = p.batchNum + 1
-				if batchInfo, err := p.handleForgeBatch(p.ctx, batchNum); err != nil {
+				batchInfo, err := p.handleForgeBatch(p.ctx, batchNum)
+				if p.ctx.Err() != nil {
+					continue
+				} else if err != nil {
 					waitDuration = p.cfg.SyncRetryInterval
 					continue
-				} else {
-					p.batchNum = batchNum
-					select {
-					case batchChSentServerProof <- batchInfo:
-					case <-p.ctx.Done():
-					}
+				}
+				p.batchNum = batchNum
+				select {
+				case batchChSentServerProof <- batchInfo:
+				case <-p.ctx.Done():
 				}
 			}
 		}

@@ -28,12 +28,14 @@ func newStateDB(t *testing.T) *statedb.LocalStateDB {
 	syncDBPath, err := ioutil.TempDir("", "tmpSyncDB")
 	require.NoError(t, err)
 	deleteme = append(deleteme, syncDBPath)
-	syncStateDB, err := statedb.NewStateDB(syncDBPath, 128, statedb.TypeSynchronizer, 48)
+	syncStateDB, err := statedb.NewStateDB(statedb.Config{Path: syncDBPath, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 48})
 	assert.NoError(t, err)
 	stateDBPath, err := ioutil.TempDir("", "tmpStateDB")
 	require.NoError(t, err)
 	deleteme = append(deleteme, stateDBPath)
-	stateDB, err := statedb.NewLocalStateDB(stateDBPath, 128, syncStateDB, statedb.TypeTxSelector, 0)
+	stateDB, err := statedb.NewLocalStateDB(statedb.Config{Path: stateDBPath, Keep: 128,
+		Type: statedb.TypeTxSelector, NLevels: 0}, syncStateDB)
 	require.NoError(t, err)
 	return stateDB
 }

@@ -27,6 +27,8 @@ PathCurrent = "current"
 	// PathLast defines the subpath of the last Batch in the subpath
 	// of the StateDB
 	PathLast = "last"
+	// DefaultKeep is the default value for the Keep parameter
+	DefaultKeep = 128
 )
 
 var (
@@ -34,16 +36,18 @@ // KeyCurrentBatch is used as key in the db to store the current BatchNum
 	KeyCurrentBatch = []byte("k:currentbatch")
 	// keyCurrentIdx is used as key in the db to store the CurrentIdx
 	keyCurrentIdx = []byte("k:idx")
+	// ErrNoLast is returned when the KVDB has been configured to not have
+	// a Last checkpoint but a Last method is used
+	ErrNoLast = fmt.Errorf("no last checkpoint")
 )
 
 // KVDB represents the Key-Value DB object
 type KVDB struct {
-	path string
-	db   *pebble.Storage
+	cfg Config
+	db  *pebble.Storage
 	// CurrentIdx holds the current Idx that the BatchBuilder is using
 	CurrentIdx   common.Idx
 	CurrentBatch common.BatchNum
-	keep         int
 	m            sync.Mutex
 	last         *Last
 }
@@ -103,23 +107,42 @@ k.db = nil
 	}
 }
 
+// Config of the KVDB
+type Config struct {
+	// Path where the checkpoints will be stored
+	Path string
+	// Keep is the number of old checkpoints to keep.  If 0, all
+	// checkpoints are kept.
+	Keep int
+	// At every checkpoint, check that there are no gaps between the
+	// checkpoints
+	NoGapsCheck bool
+	// NoLast skips having an opened DB with a checkpoint to the last
+	// batchNum for thread-safe reads.
+	NoLast bool
+}
+
 // NewKVDB creates a new KVDB, allowing to use an in-memory or in-disk storage.
 // Checkpoints older than the value defined by `keep` will be deleted.
-func NewKVDB(pathDB string, keep int) (*KVDB, error) {
+// func NewKVDB(pathDB string, keep int) (*KVDB, error) {
+func NewKVDB(cfg Config) (*KVDB, error) {
 	var sto *pebble.Storage
 	var err error
-	sto, err = pebble.NewPebbleStorage(path.Join(pathDB, PathCurrent), false)
+	sto, err = pebble.NewPebbleStorage(path.Join(cfg.Path, PathCurrent), false)
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}
 
+	var last *Last
+	if !cfg.NoLast {
+		last = &Last{
+			path: cfg.Path,
+		}
+	}
 	kvdb := &KVDB{
-		path: pathDB,
+		cfg:  cfg,
 		db:   sto,
-		keep: keep,
-		last: &Last{
-			path: pathDB,
-		},
+		last: last,
 	}
 	// load currentBatch
 	kvdb.CurrentBatch, err = kvdb.GetCurrentBatch()
@@ -137,29 +160,32 @@ return kvdb, nil
 }
 
 // LastRead is a thread-safe method to query the last KVDB
-func (kvdb *KVDB) LastRead(fn func(db *pebble.Storage) error) error {
-	kvdb.last.rw.RLock()
-	defer kvdb.last.rw.RUnlock()
-	return fn(kvdb.last.db)
+func (k *KVDB) LastRead(fn func(db *pebble.Storage) error) error {
+	if k.last == nil {
+		return tracerr.Wrap(ErrNoLast)
+	}
+	k.last.rw.RLock()
+	defer k.last.rw.RUnlock()
+	return fn(k.last.db)
 }
 
 // DB returns the *pebble.Storage from the KVDB
-func (kvdb *KVDB) DB() *pebble.Storage {
-	return kvdb.db
+func (k *KVDB) DB() *pebble.Storage {
+	return k.db
 }
 
 // StorageWithPrefix returns the db.Storage with the given prefix from the
 // current KVDB
-func (kvdb *KVDB) StorageWithPrefix(prefix []byte) db.Storage {
-	return kvdb.db.WithPrefix(prefix)
+func (k *KVDB) StorageWithPrefix(prefix []byte) db.Storage {
+	return k.db.WithPrefix(prefix)
 }
 
 // Reset resets the KVDB to the checkpoint at the given batchNum. Reset does
 // not delete the checkpoints between old current and the new current, those
 // checkpoints will remain in the storage, and eventually will be deleted when
 // MakeCheckpoint overwrites them.
-func (kvdb *KVDB) Reset(batchNum common.BatchNum) error {
-	return kvdb.reset(batchNum, true)
+func (k *KVDB) Reset(batchNum common.BatchNum) error {
+	return k.reset(batchNum, true)
 }
 
 // reset resets the KVDB to the checkpoint at the given batchNum. Reset does
@@ -167,19 +193,19 @@ // not delete the checkpoints between old current and the new current, those
 // checkpoints will remain in the storage, and eventually will be deleted when
 // MakeCheckpoint overwrites them.  `closeCurrent` will close the currently
 // opened db before doing the reset.
-func (kvdb *KVDB) reset(batchNum common.BatchNum, closeCurrent bool) error {
-	currentPath := path.Join(kvdb.path, PathCurrent)
+func (k *KVDB) reset(batchNum common.BatchNum, closeCurrent bool) error {
+	currentPath := path.Join(k.cfg.Path, PathCurrent)
 
-	if closeCurrent && kvdb.db != nil {
-		kvdb.db.Close()
-		kvdb.db = nil
+	if closeCurrent && k.db != nil {
+		k.db.Close()
+		k.db = nil
 	}
 	// remove 'current'
 	if err := os.RemoveAll(currentPath); err != nil {
 		return tracerr.Wrap(err)
 	}
 	// remove all checkpoints > batchNum
-	list, err := kvdb.ListCheckpoints()
+	list, err := k.ListCheckpoints()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -192,7 +218,7 @@ break
 		}
 	}
 	for _, bn := range list[start:] {
-		if err := kvdb.DeleteCheckpoint(common.BatchNum(bn)); err != nil {
+		if err := k.DeleteCheckpoint(common.BatchNum(bn)); err != nil {
 			return tracerr.Wrap(err)
 		}
 	}
@@ -203,23 +229,27 @@ sto, err := pebble.NewPebbleStorage(currentPath, false)
 		if err != nil {
 			return tracerr.Wrap(err)
 		}
-		kvdb.db = sto
-		kvdb.CurrentIdx = common.RollupConstReservedIDx // 255
-		kvdb.CurrentBatch = 0
-		if err := kvdb.last.setNew(); err != nil {
-			return tracerr.Wrap(err)
+		k.db = sto
+		k.CurrentIdx = common.RollupConstReservedIDx // 255
+		k.CurrentBatch = 0
+		if k.last != nil {
+			if err := k.last.setNew(); err != nil {
+				return tracerr.Wrap(err)
+			}
 		}
 
 		return nil
 	}
 
 	// copy 'batchNum' to 'current'
-	if err := kvdb.MakeCheckpointFromTo(batchNum, currentPath); err != nil {
+	if err := k.MakeCheckpointFromTo(batchNum, currentPath); err != nil {
 		return tracerr.Wrap(err)
 	}
 	// copy 'batchNum' to 'last'
-	if err := kvdb.last.set(kvdb, batchNum); err != nil {
-		return tracerr.Wrap(err)
+	if k.last != nil {
+		if err := k.last.set(k, batchNum); err != nil {
+			return tracerr.Wrap(err)
+		}
 	}
 
 	// open the new 'current'
@@ -227,15 +257,15 @@ sto, err := pebble.NewPebbleStorage(currentPath, false)
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
-	kvdb.db = sto
+	k.db = sto
 
 	// get currentBatch num
-	kvdb.CurrentBatch, err = kvdb.GetCurrentBatch()
+	k.CurrentBatch, err = k.GetCurrentBatch()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
 	// idx is obtained from the statedb reset
-	kvdb.CurrentIdx, err = kvdb.GetCurrentIdx()
+	k.CurrentIdx, err = k.GetCurrentIdx()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -245,15 +275,15 @@ }
 
 // ResetFromSynchronizer performs a reset in the KVDB getting the state from
 // synchronizerKVDB for the given batchNum.
-func (kvdb *KVDB) ResetFromSynchronizer(batchNum common.BatchNum, synchronizerKVDB *KVDB) error {
+func (k *KVDB) ResetFromSynchronizer(batchNum common.BatchNum, synchronizerKVDB *KVDB) error {
 	if synchronizerKVDB == nil {
 		return tracerr.Wrap(fmt.Errorf("synchronizerKVDB can not be nil"))
 	}
 
-	currentPath := path.Join(kvdb.path, PathCurrent)
-	if kvdb.db != nil {
-		kvdb.db.Close()
-		kvdb.db = nil
+	currentPath := path.Join(k.cfg.Path, PathCurrent)
+	if k.db != nil {
+		k.db.Close()
+		k.db = nil
 	}
 
 	// remove 'current'
@@ -261,12 +291,12 @@ if err := os.RemoveAll(currentPath); err != nil {
 		return tracerr.Wrap(err)
 	}
 	// remove all checkpoints
-	list, err := kvdb.ListCheckpoints()
+	list, err := k.ListCheckpoints()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
 	for _, bn := range list {
-		if err := kvdb.DeleteCheckpoint(common.BatchNum(bn)); err != nil {
+		if err := k.DeleteCheckpoint(common.BatchNum(bn)); err != nil {
 			return tracerr.Wrap(err)
 		}
 	}
@@ -277,14 +307,14 @@ sto, err := pebble.NewPebbleStorage(currentPath, false)
 		if err != nil {
 			return tracerr.Wrap(err)
 		}
-		kvdb.db = sto
-		kvdb.CurrentIdx = common.RollupConstReservedIDx // 255
-		kvdb.CurrentBatch = 0
+		k.db = sto
+		k.CurrentIdx = common.RollupConstReservedIDx // 255
+		k.CurrentBatch = 0
 
 		return nil
 	}
 
-	checkpointPath := path.Join(kvdb.path, fmt.Sprintf("%s%d", PathBatchNum, batchNum))
+	checkpointPath := path.Join(k.cfg.Path, fmt.Sprintf("%s%d", PathBatchNum, batchNum))
 
 	// copy synchronizer'BatchNumX' to 'BatchNumX'
 	if err := synchronizerKVDB.MakeCheckpointFromTo(batchNum, checkpointPath); err != nil {
@@ -292,7 +322,7 @@ return tracerr.Wrap(err)
 	}
 
 	// copy 'BatchNumX' to 'current'
-	err = kvdb.MakeCheckpointFromTo(batchNum, currentPath)
+	err = k.MakeCheckpointFromTo(batchNum, currentPath)
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -302,15 +332,15 @@ sto, err := pebble.NewPebbleStorage(currentPath, false)
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
-	kvdb.db = sto
+	k.db = sto
 
 	// get currentBatch num
-	kvdb.CurrentBatch, err = kvdb.GetCurrentBatch()
+	k.CurrentBatch, err = k.GetCurrentBatch()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
 	// get currentIdx
-	kvdb.CurrentIdx, err = kvdb.GetCurrentIdx()
+	k.CurrentIdx, err = k.GetCurrentIdx()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -319,8 +349,8 @@ return nil
 }
 
 // GetCurrentBatch returns the current BatchNum stored in the KVDB
-func (kvdb *KVDB) GetCurrentBatch() (common.BatchNum, error) {
-	cbBytes, err := kvdb.db.Get(KeyCurrentBatch)
+func (k *KVDB) GetCurrentBatch() (common.BatchNum, error) {
+	cbBytes, err := k.db.Get(KeyCurrentBatch)
 	if tracerr.Unwrap(err) == db.ErrNotFound {
 		return 0, nil
 	}
@@ -331,12 +361,12 @@ return common.BatchNumFromBytes(cbBytes)
 }
 
 // setCurrentBatch stores the current BatchNum in the KVDB
-func (kvdb *KVDB) setCurrentBatch() error {
-	tx, err := kvdb.db.NewTx()
+func (k *KVDB) setCurrentBatch() error {
+	tx, err := k.db.NewTx()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
-	err = tx.Put(KeyCurrentBatch, kvdb.CurrentBatch.Bytes())
+	err = tx.Put(KeyCurrentBatch, k.CurrentBatch.Bytes())
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -347,9 +377,9 @@ return nil
 }
 
 // GetCurrentIdx returns the stored Idx from the KVDB, which is the last Idx
-// used for an Account in the KVDB.
-func (kvdb *KVDB) GetCurrentIdx() (common.Idx, error) {
-	idxBytes, err := kvdb.db.Get(keyCurrentIdx)
+// used for an Account in the k.
+func (k *KVDB) GetCurrentIdx() (common.Idx, error) {
+	idxBytes, err := k.db.Get(keyCurrentIdx)
 	if tracerr.Unwrap(err) == db.ErrNotFound {
 		return common.RollupConstReservedIDx, nil // 255, nil
 	}
@@ -360,10 +390,10 @@ return common.IdxFromBytes(idxBytes[:])
 }
 
 // SetCurrentIdx stores Idx in the KVDB
-func (kvdb *KVDB) SetCurrentIdx(idx common.Idx) error {
-	kvdb.CurrentIdx = idx
+func (k *KVDB) SetCurrentIdx(idx common.Idx) error {
+	k.CurrentIdx = idx
 
-	tx, err := kvdb.db.NewTx()
+	tx, err := k.db.NewTx()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -383,14 +413,14 @@ }
 
 // MakeCheckpoint does a checkpoint at the given batchNum in the defined path.
 // Internally this advances & stores the current BatchNum, and then stores a
-// Checkpoint of the current state of the KVDB.
-func (kvdb *KVDB) MakeCheckpoint() error {
+// Checkpoint of the current state of the k.
+func (k *KVDB) MakeCheckpoint() error {
 	// advance currentBatch
-	kvdb.CurrentBatch++
+	k.CurrentBatch++
 
-	checkpointPath := path.Join(kvdb.path, fmt.Sprintf("%s%d", PathBatchNum, kvdb.CurrentBatch))
+	checkpointPath := path.Join(k.cfg.Path, fmt.Sprintf("%s%d", PathBatchNum, k.CurrentBatch))
 
-	if err := kvdb.setCurrentBatch(); err != nil {
+	if err := k.setCurrentBatch(); err != nil {
 		return tracerr.Wrap(err)
 	}
 
@@ -404,15 +434,17 @@ return tracerr.Wrap(err)
 	}
 
 	// execute Checkpoint
-	if err := kvdb.db.Pebble().Checkpoint(checkpointPath); err != nil {
+	if err := k.db.Pebble().Checkpoint(checkpointPath); err != nil {
 		return tracerr.Wrap(err)
 	}
 	// copy 'CurrentBatch' to 'last'
-	if err := kvdb.last.set(kvdb, kvdb.CurrentBatch); err != nil {
-		return tracerr.Wrap(err)
+	if k.last != nil {
+		if err := k.last.set(k, k.CurrentBatch); err != nil {
+			return tracerr.Wrap(err)
+		}
 	}
 	// delete old checkpoints
-	if err := kvdb.deleteOldCheckpoints(); err != nil {
+	if err := k.deleteOldCheckpoints(); err != nil {
 		return tracerr.Wrap(err)
 	}
 
@@ -420,8 +452,8 @@ return nil
 }
 
 // DeleteCheckpoint removes if exist the checkpoint of the given batchNum
-func (kvdb *KVDB) DeleteCheckpoint(batchNum common.BatchNum) error {
-	checkpointPath := path.Join(kvdb.path, fmt.Sprintf("%s%d", PathBatchNum, batchNum))
+func (k *KVDB) DeleteCheckpoint(batchNum common.BatchNum) error {
+	checkpointPath := path.Join(k.cfg.Path, fmt.Sprintf("%s%d", PathBatchNum, batchNum))
 
 	if _, err := os.Stat(checkpointPath); os.IsNotExist(err) {
 		return tracerr.Wrap(fmt.Errorf("Checkpoint with batchNum %d does not exist in DB", batchNum))
@@ -432,8 +464,8 @@ }
 
 // ListCheckpoints returns the list of batchNums of the checkpoints, sorted.
 // If there's a gap between the list of checkpoints, an error is returned.
-func (kvdb *KVDB) ListCheckpoints() ([]int, error) {
-	files, err := ioutil.ReadDir(kvdb.path)
+func (k *KVDB) ListCheckpoints() ([]int, error) {
+	files, err := ioutil.ReadDir(k.cfg.Path)
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}
@@ -450,12 +482,12 @@ checkpoints = append(checkpoints, checkpoint)
 		}
 	}
 	sort.Ints(checkpoints)
-	if len(checkpoints) > 0 {
+	if !k.cfg.NoGapsCheck && len(checkpoints) > 0 {
 		first := checkpoints[0]
 		for _, checkpoint := range checkpoints[1:] {
 			first++
 			if checkpoint != first {
-				log.Errorw("GAP", "checkpoints", checkpoints)
+				log.Errorw("gap between checkpoints", "checkpoints", checkpoints)
 				return nil, tracerr.Wrap(fmt.Errorf("checkpoint gap at %v", checkpoint))
 			}
 		}
@@ -465,14 +497,14 @@ }
 
 // deleteOldCheckpoints deletes old checkpoints when there are more than
 // `s.keep` checkpoints
-func (kvdb *KVDB) deleteOldCheckpoints() error {
-	list, err := kvdb.ListCheckpoints()
+func (k *KVDB) deleteOldCheckpoints() error {
+	list, err := k.ListCheckpoints()
 	if err != nil {
 		return tracerr.Wrap(err)
 	}
-	if len(list) > kvdb.keep {
-		for _, checkpoint := range list[:len(list)-kvdb.keep] {
-			if err := kvdb.DeleteCheckpoint(common.BatchNum(checkpoint)); err != nil {
+	if k.cfg.Keep > 0 && len(list) > k.cfg.Keep {
+		for _, checkpoint := range list[:len(list)-k.cfg.Keep] {
+			if err := k.DeleteCheckpoint(common.BatchNum(checkpoint)); err != nil {
 				return tracerr.Wrap(err)
 			}
 		}
@@ -483,8 +515,8 @@
 // MakeCheckpointFromTo makes a checkpoint from the current db at fromBatchNum
 // to the dest folder.  This method is locking, so it can be called from
 // multiple places at the same time.
-func (kvdb *KVDB) MakeCheckpointFromTo(fromBatchNum common.BatchNum, dest string) error {
-	source := path.Join(kvdb.path, fmt.Sprintf("%s%d", PathBatchNum, fromBatchNum))
+func (k *KVDB) MakeCheckpointFromTo(fromBatchNum common.BatchNum, dest string) error {
+	source := path.Join(k.cfg.Path, fmt.Sprintf("%s%d", PathBatchNum, fromBatchNum))
 	if _, err := os.Stat(source); os.IsNotExist(err) {
 		// if kvdb does not have checkpoint at batchNum, return err
 		return tracerr.Wrap(fmt.Errorf("Checkpoint \"%v\" does not exist", source))
@@ -494,8 +526,8 @@ // places at the same time for the same stateDB.  This allows the
 	// synchronizer to do a reset to a batchNum at the same time as the
 	// pipeline is doing a txSelector.Reset and batchBuilder.Reset from
 	// synchronizer to the same batchNum
-	kvdb.m.Lock()
-	defer kvdb.m.Unlock()
+	k.m.Lock()
+	defer k.m.Unlock()
 	return pebbleMakeCheckpoint(source, dest)
 }
 
@@ -525,10 +557,12 @@ return nil
 }
 
 // Close the DB
-func (kvdb *KVDB) Close() {
-	if kvdb.db != nil {
-		kvdb.db.Close()
-		kvdb.db = nil
+func (k *KVDB) Close() {
+	if k.db != nil {
+		k.db.Close()
+		k.db = nil
 	}
-	kvdb.last.close()
+	if k.last != nil {
+		k.last.close()
+	}
 }

@@ -37,7 +37,7 @@ dir, err := ioutil.TempDir("", "sdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	db, err := NewKVDB(dir, 128)
+	db, err := NewKVDB(Config{Path: dir, Keep: 128})
 	require.NoError(t, err)
 
 	// add test key-values
@@ -72,7 +72,7 @@ // 'BatchNum3', from where the 'current' is a copy)
 	err = db.Reset(3)
 	require.NoError(t, err)
 
-	printCheckpoints(t, db.path)
+	printCheckpoints(t, db.cfg.Path)
 
 	// check that currentBatch is as expected after Reset
 	cb, err = db.GetCurrentBatch()
@@ -99,7 +99,7 @@ // Create a new KVDB which will get Reset from the initial KVDB
 	dirLocal, err := ioutil.TempDir("", "ldb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dirLocal))
-	ldb, err := NewKVDB(dirLocal, 128)
+	ldb, err := NewKVDB(Config{Path: dirLocal, Keep: 128})
 	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
@@ -120,7 +120,7 @@ // Create a 3rd KVDB which will get Reset from the initial KVDB
 	dirLocal2, err := ioutil.TempDir("", "ldb2")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dirLocal2))
-	ldb2, err := NewKVDB(dirLocal2, 128)
+	ldb2, err := NewKVDB(Config{Path: dirLocal2, Keep: 128})
 	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
@@ -139,9 +139,9 @@ assert.Equal(t, common.BatchNum(5), cb)
 
 	debug := false
 	if debug {
-		printCheckpoints(t, db.path)
-		printCheckpoints(t, ldb.path)
-		printCheckpoints(t, ldb2.path)
+		printCheckpoints(t, db.cfg.Path)
+		printCheckpoints(t, ldb.cfg.Path)
+		printCheckpoints(t, ldb2.cfg.Path)
 	}
 }
 
@@ -150,7 +150,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	db, err := NewKVDB(dir, 128)
+	db, err := NewKVDB(Config{Path: dir, Keep: 128})
 	require.NoError(t, err)
 
 	numCheckpoints := 16
@@ -181,7 +181,7 @@ require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
-	db, err := NewKVDB(dir, keep)
+	db, err := NewKVDB(Config{Path: dir, Keep: keep})
 	require.NoError(t, err)
 
 	numCheckpoints := 32
@@ -202,7 +202,7 @@ require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
-	db, err := NewKVDB(dir, keep)
+	db, err := NewKVDB(Config{Path: dir, Keep: keep})
 	require.NoError(t, err)
 
 	idx, err := db.GetCurrentIdx()
@@ -211,7 +211,7 @@ assert.Equal(t, common.Idx(255), idx)
 
 	db.Close()
 
-	db, err = NewKVDB(dir, keep)
+	db, err = NewKVDB(Config{Path: dir, Keep: keep})
 	require.NoError(t, err)
 
 	idx, err = db.GetCurrentIdx()
@@ -227,7 +227,7 @@ assert.Equal(t, common.Idx(255), idx)
 
 	db.Close()
 
-	db, err = NewKVDB(dir, keep)
+	db, err = NewKVDB(Config{Path: dir, Keep: keep})
 	require.NoError(t, err)
 
 	idx, err = db.GetCurrentIdx()

@@ -52,19 +52,40 @@ TypeTxSelector = "txselector"
 	// TypeBatchBuilder defines a StateDB used by the BatchBuilder, that
 	// generates the ExitTree and the ZKInput when processing the txs
 	TypeBatchBuilder = "batchbuilder"
+	// MaxNLevels is the maximum value of NLevels for the merkle tree,
+	// which comes from the fact that AccountIdx has 48 bits.
+	MaxNLevels = 48
 )
 
 // TypeStateDB determines the type of StateDB
 type TypeStateDB string
 
+// Config of the StateDB
+type Config struct {
+	// Path where the checkpoints will be stored
+	Path string
+	// Keep is the number of old checkpoints to keep.  If 0, all
+	// checkpoints are kept.
+	Keep int
+	// NoLast skips having an opened DB with a checkpoint to the last
+	// batchNum for thread-safe reads.
+	NoLast bool
+	// Type of StateDB (
+	Type TypeStateDB
+	// NLevels is the number of merkle tree levels in case the Type uses a
+	// merkle tree.  If the Type doesn't use a merkle tree, NLevels should
+	// be 0.
+	NLevels int
+	// At every checkpoint, check that there are no gaps between the
+	// checkpoints
+	noGapsCheck bool
+}
+
 // StateDB represents the StateDB object
 type StateDB struct {
-	path    string
-	Typ     TypeStateDB
-	db      *kvdb.KVDB
-	nLevels int
-	MT      *merkletree.MerkleTree
-	keep    int
+	cfg Config
+	db  *kvdb.KVDB
+	MT  *merkletree.MerkleTree
 }
 
 // Last offers a subset of view methods of the StateDB that can be
@@ -104,36 +125,40 @@
 // NewStateDB creates a new StateDB, allowing to use an in-memory or in-disk
 // storage.  Checkpoints older than the value defined by `keep` will be
 // deleted.
-func NewStateDB(pathDB string, keep int, typ TypeStateDB, nLevels int) (*StateDB, error) {
+// func NewStateDB(pathDB string, keep int, typ TypeStateDB, nLevels int) (*StateDB, error) {
+func NewStateDB(cfg Config) (*StateDB, error) {
 	var kv *kvdb.KVDB
 	var err error
 
-	kv, err = kvdb.NewKVDB(pathDB, keep)
+	kv, err = kvdb.NewKVDB(kvdb.Config{Path: cfg.Path, Keep: cfg.Keep,
+		NoGapsCheck: cfg.noGapsCheck, NoLast: cfg.NoLast})
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}
 
 	var mt *merkletree.MerkleTree = nil
-	if typ == TypeSynchronizer || typ == TypeBatchBuilder {
-		mt, err = merkletree.NewMerkleTree(kv.StorageWithPrefix(PrefixKeyMT), nLevels)
+	if cfg.Type == TypeSynchronizer || cfg.Type == TypeBatchBuilder {
+		mt, err = merkletree.NewMerkleTree(kv.StorageWithPrefix(PrefixKeyMT), cfg.NLevels)
 		if err != nil {
 			return nil, tracerr.Wrap(err)
 		}
 	}
-	if typ == TypeTxSelector && nLevels != 0 {
+	if cfg.Type == TypeTxSelector && cfg.NLevels != 0 {
 		return nil, tracerr.Wrap(fmt.Errorf("invalid StateDB parameters: StateDB type==TypeStateDB can not have nLevels!=0"))
 	}
 
 	return &StateDB{
-		path:    pathDB,
-		db:      kv,
-		nLevels: nLevels,
-		MT:      mt,
-		Typ:     typ,
-		keep:    keep,
+		cfg: cfg,
+		db:  kv,
+		MT:  mt,
 	}, nil
 }
 
+// Type returns the StateDB configured Type
+func (s *StateDB) Type() TypeStateDB {
+	return s.cfg.Type
+}
+
 // LastRead is a thread-safe method to query the last checkpoint of the StateDB
 // via the Last type methods
 func (s *StateDB) LastRead(fn func(sdbLast *Last) error) error {
@@ -179,7 +204,7 @@ // checkpoint of the StateDB.
 func (s *StateDB) LastMTGetRoot() (*big.Int, error) {
 	var root *big.Int
 	if err := s.LastRead(func(sdb *Last) error {
-		mt, err := merkletree.NewMerkleTree(sdb.DB().WithPrefix(PrefixKeyMT), s.nLevels)
+		mt, err := merkletree.NewMerkleTree(sdb.DB().WithPrefix(PrefixKeyMT), s.cfg.NLevels)
 		if err != nil {
 			return tracerr.Wrap(err)
 		}
@@ -195,7 +220,7 @@ // MakeCheckpoint does a checkpoint at the given batchNum in the defined path.
 // Internally this advances & stores the current BatchNum, and then stores a
 // Checkpoint of the current state of the StateDB.
 func (s *StateDB) MakeCheckpoint() error {
-	log.Debugw("Making StateDB checkpoint", "batch", s.CurrentBatch()+1, "type", s.Typ)
+	log.Debugw("Making StateDB checkpoint", "batch", s.CurrentBatch()+1, "type", s.cfg.Type)
 	return s.db.MakeCheckpoint()
 }
 
@@ -230,7 +255,7 @@ // does not delete the checkpoints between old current and the new current,
 // those checkpoints will remain in the storage, and eventually will be
 // deleted when MakeCheckpoint overwrites them.
 func (s *StateDB) Reset(batchNum common.BatchNum) error {
-	log.Debugw("Making StateDB Reset", "batch", batchNum, "type", s.Typ)
+	log.Debugw("Making StateDB Reset", "batch", batchNum, "type", s.cfg.Type)
 	if err := s.db.Reset(batchNum); err != nil {
 		return tracerr.Wrap(err)
 	}
@@ -460,9 +485,10 @@
 // NewLocalStateDB returns a new LocalStateDB connected to the given
 // synchronizerDB.  Checkpoints older than the value defined by `keep` will be
 // deleted.
-func NewLocalStateDB(path string, keep int, synchronizerDB *StateDB, typ TypeStateDB,
-	nLevels int) (*LocalStateDB, error) {
-	s, err := NewStateDB(path, keep, typ, nLevels)
+func NewLocalStateDB(cfg Config, synchronizerDB *StateDB) (*LocalStateDB, error) {
+	cfg.noGapsCheck = true
+	cfg.NoLast = true
+	s, err := NewStateDB(cfg)
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}

@@ -45,7 +45,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 
 	// test values
@@ -78,7 +78,7 @@ sdb.Close()
 
 	// call NewStateDB which should get the db at the last checkpoint state
 	// executing a Reset (discarding the last 'testkey0'&'testvalue0' data)
-	sdb, err = NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err = NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 	v, err = sdb.db.DB().Get(k0)
 	assert.NotNil(t, err)
@@ -158,7 +158,7 @@ sdb.Close()
 
 	// call NewStateDB which should get the db at the last checkpoint state
 	// executing a Reset (discarding the last 'testkey1'&'testvalue1' data)
-	sdb, err = NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err = NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 
 	bn, err = sdb.getCurrentBatch()
@@ -182,7 +182,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 
 	// create test accounts
@@ -236,7 +236,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	// create test accounts
@@ -290,7 +290,7 @@ dir, err := ioutil.TempDir("", "sdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	err = sdb.Reset(0)
@@ -335,7 +335,7 @@ require.NoError(t, err)
 		assert.Equal(t, common.BatchNum(i+1), cb)
 	}
 
-	// printCheckpoints(t, sdb.path)
+	// printCheckpoints(t, sdb.cfg.Path)
 
 	// reset checkpoint
 	err = sdb.Reset(3)
@@ -371,7 +371,7 @@ // Create a LocalStateDB from the initial StateDB
 	dirLocal, err := ioutil.TempDir("", "ldb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dirLocal))
-	ldb, err := NewLocalStateDB(dirLocal, 128, sdb, TypeBatchBuilder, 32)
+	ldb, err := NewLocalStateDB(Config{Path: dirLocal, Keep: 128, Type: TypeBatchBuilder, NLevels: 32}, sdb)
 	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
@@ -392,7 +392,7 @@ // Create a 2nd LocalStateDB from the initial StateDB
 	dirLocal2, err := ioutil.TempDir("", "ldb2")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dirLocal2))
-	ldb2, err := NewLocalStateDB(dirLocal2, 128, sdb, TypeBatchBuilder, 32)
+	ldb2, err := NewLocalStateDB(Config{Path: dirLocal2, Keep: 128, Type: TypeBatchBuilder, NLevels: 32}, sdb)
 	require.NoError(t, err)
 
 	// get checkpoint 4 from sdb (StateDB) to ldb (LocalStateDB)
@@ -409,9 +409,9 @@ assert.Equal(t, common.BatchNum(5), cb)
 
 	debug := false
 	if debug {
-		printCheckpoints(t, sdb.path)
-		printCheckpoints(t, ldb.path)
-		printCheckpoints(t, ldb2.path)
+		printCheckpoints(t, sdb.cfg.Path)
+		printCheckpoints(t, ldb.cfg.Path)
+		printCheckpoints(t, ldb2.cfg.Path)
 	}
 }
 
@@ -419,7 +419,7 @@ func TestStateDBGetAccounts(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 
-	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 
 	// create test accounts
@@ -466,7 +466,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	ay0 := new(big.Int).Sub(new(big.Int).Exp(big.NewInt(2), big.NewInt(253), nil), big.NewInt(1))
@@ -540,7 +540,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	numCheckpoints := 16
@@ -573,7 +573,7 @@ require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
-	sdb, err := NewStateDB(dir, keep, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	numCheckpoints := 32
@@ -594,7 +594,7 @@ require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
-	sdb, err := NewStateDB(dir, keep, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	idx := sdb.CurrentIdx()
@@ -602,7 +602,7 @@ assert.Equal(t, common.Idx(255), idx)
 
 	sdb.Close()
 
-	sdb, err = NewStateDB(dir, keep, TypeSynchronizer, 32)
+	sdb, err = NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	idx = sdb.CurrentIdx()
@@ -616,7 +616,7 @@ assert.Equal(t, common.Idx(255), idx)
 
 	sdb.Close()
 
-	sdb, err = NewStateDB(dir, keep, TypeSynchronizer, 32)
+	sdb, err = NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	idx = sdb.CurrentIdx()
@@ -629,7 +629,7 @@ require.NoError(t, err)
 	defer require.NoError(t, os.RemoveAll(dir))
 
 	keep := 16
-	sdb, err := NewStateDB(dir, keep, TypeSynchronizer, 32)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	err = sdb.MakeCheckpoint()

@@ -18,7 +18,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := NewStateDB(dir, 128, TypeTxSelector, 0)
+	sdb, err := NewStateDB(Config{Path: dir, Keep: 128, Type: TypeTxSelector, NLevels: 0})
 	assert.NoError(t, err)
 
 	var sk babyjub.PrivateKey

@@ -164,8 +164,12 @@ if cfg.StateDB.Keep < safeStateDBKeep {
 		return nil, tracerr.Wrap(fmt.Errorf("cfg.StateDB.Keep = %v < %v, which is unsafe",
 			cfg.StateDB.Keep, safeStateDBKeep))
 	}
-	stateDB, err := statedb.NewStateDB(cfg.StateDB.Path, cfg.StateDB.Keep,
-		statedb.TypeSynchronizer, 32)
+	stateDB, err := statedb.NewStateDB(statedb.Config{
+		Path:    cfg.StateDB.Path,
+		Keep:    cfg.StateDB.Keep,
+		Type:    statedb.TypeSynchronizer,
+		NLevels: statedb.MaxNLevels,
+	})
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}

@@ -307,7 +307,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	deleteme = append(deleteme, dir)
 
-	stateDB, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	stateDB, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128, Type: statedb.TypeSynchronizer, NLevels: 32})
 	require.NoError(t, err)
 
 	// Init History DB

@@ -44,7 +44,7 @@ func TestDebugAPI(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.Nil(t, err)
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128, Type: statedb.TypeSynchronizer, NLevels: 32})
 	require.Nil(t, err)
 	err = sdb.MakeCheckpoint() // Make a checkpoint to increment the batchNum
 	require.Nil(t, err)

@@ -80,7 +80,8 @@
 	dir, err := ioutil.TempDir("", "tmpSyncDB")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
-	syncStateDB, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 0)
+	syncStateDB, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 0})
 	require.NoError(t, err)
 
 	txselDir, err := ioutil.TempDir("", "tmpTxSelDB")

@@ -50,7 +50,7 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, typ, NLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128, Type: typ, NLevels: NLevels})
 	require.NoError(t, err)
 	return sdb
 }

@@ -127,7 +127,7 @@ }
 
 	exits := make([]processedExit, nTx)
 
-	if tp.s.Typ == statedb.TypeBatchBuilder {
+	if tp.s.Type() == statedb.TypeBatchBuilder {
 		tp.zki = common.NewZKInputs(tp.config.ChainID, tp.config.MaxTx, tp.config.MaxL1Tx,
 			tp.config.MaxFeeTx, tp.config.NLevels, (tp.s.CurrentBatch() + 1).BigInt())
 		tp.zki.OldLastIdx = tp.s.CurrentIdx().BigInt()
@@ -137,7 +137,7 @@ }
 
 	// TBD if ExitTree is only in memory or stored in disk, for the moment
 	// is only needed in memory
-	if tp.s.Typ == statedb.TypeSynchronizer || tp.s.Typ == statedb.TypeBatchBuilder {
+	if tp.s.Type() == statedb.TypeSynchronizer || tp.s.Type() == statedb.TypeBatchBuilder {
 		tmpDir, err := ioutil.TempDir("", "hermez-statedb-exittree")
 		if err != nil {
 			return nil, tracerr.Wrap(err)
@@ -166,7 +166,7 @@ &l1usertxs[i])
 		if err != nil {
 			return nil, tracerr.Wrap(err)
 		}
-		if tp.s.Typ == statedb.TypeSynchronizer {
+		if tp.s.Type() == statedb.TypeSynchronizer {
 			if createdAccount != nil {
 				createdAccounts = append(createdAccounts, *createdAccount)
 				l1usertxs[i].EffectiveFromIdx = createdAccount.Idx
@@ -195,7 +195,7 @@ if exitIdx == nil {
 				tp.zki.ISExitRoot[tp.i] = exitTree.Root().BigInt()
 			}
 		}
-		if tp.s.Typ == statedb.TypeSynchronizer || tp.s.Typ == statedb.TypeBatchBuilder {
+		if tp.s.Type() == statedb.TypeSynchronizer || tp.s.Type() == statedb.TypeBatchBuilder {
 			if exitIdx != nil && exitTree != nil {
 				exits[tp.i] = processedExit{
 					exit:    true,
@@ -217,7 +217,7 @@ }
 		if exitIdx != nil {
 			log.Error("Unexpected Exit in L1CoordinatorTx")
 		}
-		if tp.s.Typ == statedb.TypeSynchronizer {
+		if tp.s.Type() == statedb.TypeSynchronizer {
 			if createdAccount != nil {
 				createdAccounts = append(createdAccounts, *createdAccount)
 				l1coordinatortxs[i].EffectiveFromIdx = createdAccount.Idx
@@ -276,7 +276,7 @@ }
 	// collectedFees will contain the amount of fee collected for each
 	// TokenID
 	var collectedFees map[common.TokenID]*big.Int
-	if tp.s.Typ == statedb.TypeSynchronizer || tp.s.Typ == statedb.TypeBatchBuilder {
+	if tp.s.Type() == statedb.TypeSynchronizer || tp.s.Type() == statedb.TypeBatchBuilder {
 		collectedFees = make(map[common.TokenID]*big.Int)
 		for tokenID := range coordIdxsMap {
 			collectedFees[tokenID] = big.NewInt(0)
@@ -317,7 +317,7 @@ tp.zki.ISExitRoot[tp.i] = exitTree.Root().BigInt()
 				}
 			}
 		}
-		if tp.s.Typ == statedb.TypeSynchronizer || tp.s.Typ == statedb.TypeBatchBuilder {
+		if tp.s.Type() == statedb.TypeSynchronizer || tp.s.Type() == statedb.TypeBatchBuilder {
 			if exitIdx != nil && exitTree != nil {
 				exits[tp.i] = processedExit{
 					exit:    true,
@@ -401,7 +401,7 @@ tp.zki.FeeIdxs[i] = coordIdxs[i].BigInt()
 		}
 	}
 
-	if tp.s.Typ == statedb.TypeTxSelector {
+	if tp.s.Type() == statedb.TypeTxSelector {
 		return nil, nil
 	}
 
@@ -436,8 +436,8 @@ *prevExit = ei
 		}
 	}
 
-	if tp.s.Typ == statedb.TypeSynchronizer {
-		// return exitInfos, createdAccounts and collectedFees, so Synchronizer will
+	if tp.s.Type() == statedb.TypeSynchronizer {
+		// retuTypeexitInfos, createdAccounts and collectedFees, so Synchronizer will
 		// be able to store it into HistoryDB for the concrete BatchNum
 		return &ProcessTxOutput{
 			ZKInputs:           nil,
@@ -588,7 +588,7 @@ default:
 	}
 
 	var createdAccount *common.Account
-	if tp.s.Typ == statedb.TypeSynchronizer &&
+	if tp.s.Type() == statedb.TypeSynchronizer &&
 		(tx.Type == common.TxTypeCreateAccountDeposit ||
 			tx.Type == common.TxTypeCreateAccountDepositTransfer) {
 		var err error
@@ -612,8 +612,8 @@ tx *common.PoolL2Tx) (*common.Idx, *common.Account, bool, error) {
 	var err error
 	// if tx.ToIdx==0, get toIdx by ToEthAddr or ToBJJ
 	if tx.ToIdx == common.Idx(0) && tx.AuxToIdx == common.Idx(0) {
-		if tp.s.Typ == statedb.TypeSynchronizer {
-			// this should never be reached
+		if tp.s.Type() == statedb.TypeSynchronizer {
+			// thisTypeould never be reached
 			log.Error("WARNING: In StateDB with Synchronizer mode L2.ToIdx can't be 0")
 			return nil, nil, false, tracerr.Wrap(fmt.Errorf("In StateDB with Synchronizer mode L2.ToIdx can't be 0"))
 		}
@@ -676,8 +676,8 @@ tp.zki.R8y[tp.i] = signature.R8.Y
 	}
 
 	// if StateDB type==TypeSynchronizer, will need to add Nonce
-	if tp.s.Typ == statedb.TypeSynchronizer {
-		// as type==TypeSynchronizer, always tx.ToIdx!=0
+	if tp.s.Type() == statedb.TypeSynchronizer {
+		// as tType==TypeSynchronizer, always tx.ToIdx!=0
 		acc, err := tp.s.GetAccount(tx.FromIdx)
 		if err != nil {
 			log.Errorw("GetAccount", "fromIdx", tx.FromIdx, "err", err)
@@ -889,8 +889,8 @@ // accumulate the fee for the Coord account
 			accumulated := tp.AccumulatedFees[accCoord.Idx]
 			accumulated.Add(accumulated, fee)
 
-			if tp.s.Typ == statedb.TypeSynchronizer ||
-				tp.s.Typ == statedb.TypeBatchBuilder {
+			if tp.s.Type() == statedb.TypeSynchronizer ||
+				tp.s.Type() == statedb.TypeBatchBuilder {
 				collected := collectedFees[accCoord.TokenID]
 				collected.Add(collected, fee)
 			}
@@ -1094,8 +1094,8 @@ // accumulate the fee for the Coord account
 			accumulated := tp.AccumulatedFees[accCoord.Idx]
 			accumulated.Add(accumulated, fee)
 
-			if tp.s.Typ == statedb.TypeSynchronizer ||
-				tp.s.Typ == statedb.TypeBatchBuilder {
+			if tp.s.Type() == statedb.TypeSynchronizer ||
+				tp.s.Type() == statedb.TypeBatchBuilder {
 				collected := collectedFees[accCoord.TokenID]
 				collected.Add(collected, fee)
 			}

@@ -36,7 +36,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 32})
 	assert.NoError(t, err)
 
 	set := `
@@ -212,7 +213,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 32})
 	assert.NoError(t, err)
 
 	chainID := uint16(0)
@@ -358,7 +360,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 32})
 	assert.NoError(t, err)
 
 	chainID := uint16(0)
@@ -489,7 +492,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: 32})
 	assert.NoError(t, err)
 
 	chainID := uint16(0)
@@ -580,7 +584,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: 32})
 	assert.NoError(t, err)
 
 	// same values than in the js test
@@ -631,7 +636,8 @@ require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	assert.NoError(t, err)
 
 	users := txsets.GenerateJsUsers(t)
@@ -700,7 +706,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: 32})
 	assert.NoError(t, err)
 
 	chainID := uint16(1)
@@ -798,7 +805,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeSynchronizer, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 32})
 	assert.NoError(t, err)
 
 	chainID := uint16(1)
@@ -865,7 +873,8 @@ dir2, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir2))
 
-	sdb2, err := statedb.NewStateDB(dir2, 128, statedb.TypeSynchronizer, 32)
+	sdb2, err := statedb.NewStateDB(statedb.Config{Path: dir2, Keep: 128,
+		Type: statedb.TypeSynchronizer, NLevels: 32})
 	assert.NoError(t, err)
 
 	tc = til.NewContext(chainID, common.RollupConstMaxL1UserTx)

@@ -41,7 +41,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: 32})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -90,7 +91,8 @@ dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, 32)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: 32})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -149,7 +151,8 @@ defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
 
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -266,7 +269,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -322,7 +326,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -385,7 +390,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -456,7 +462,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -527,7 +534,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -598,7 +606,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)
@@ -661,7 +670,8 @@ require.NoError(t, err)
 	defer assert.Nil(t, os.RemoveAll(dir))
 
 	nLevels := 16
-	sdb, err := statedb.NewStateDB(dir, 128, statedb.TypeBatchBuilder, nLevels)
+	sdb, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeBatchBuilder, NLevels: nLevels})
 	require.NoError(t, err)
 
 	chainID := uint16(0)

@@ -10,6 +10,7 @@ "sort"
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/db/kvdb"
 	"github.com/hermeznetwork/hermez-node/db/l2db"
 	"github.com/hermeznetwork/hermez-node/db/statedb"
 	"github.com/hermeznetwork/hermez-node/log"
@@ -62,8 +63,14 @@
 // NewTxSelector returns a *TxSelector
 func NewTxSelector(coordAccount *CoordAccount, dbpath string,
 	synchronizerStateDB *statedb.StateDB, l2 *l2db.L2DB) (*TxSelector, error) {
-	localAccountsDB, err := statedb.NewLocalStateDB(dbpath, 128,
-		synchronizerStateDB, statedb.TypeTxSelector, 0) // without merkletree
+	localAccountsDB, err := statedb.NewLocalStateDB(
+		statedb.Config{
+			Path:    dbpath,
+			Keep:    kvdb.DefaultKeep,
+			Type:    statedb.TypeTxSelector,
+			NLevels: 0,
+		},
+		synchronizerStateDB) // without merkletree
 	if err != nil {
 		return nil, tracerr.Wrap(err)
 	}

@@ -34,7 +34,8 @@
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)
 	defer assert.NoError(t, os.RemoveAll(dir))
-	syncStateDB, err := statedb.NewStateDB(dir, 128, statedb.TypeTxSelector, 0)
+	syncStateDB, err := statedb.NewStateDB(statedb.Config{Path: dir, Keep: 128,
+		Type: statedb.TypeTxSelector, NLevels: 0})
 	require.NoError(t, err)
 
 	txselDir, err := ioutil.TempDir("", "tmpTxSelDB")