diff --git a/electrum/address_synchronizer.py b/electrum/address_synchronizer.py
index 054a337ab..2b54b395d 100644
--- a/electrum/address_synchronizer.py
+++ b/electrum/address_synchronizer.py
@@ -168,7 +168,7 @@ class AddressSynchronizer(PrintError):
 
     def add_address(self, address):
         if not self.db.get_addr_history(address):
-            self.db.history[address] = []
+            #self.db.history[address] = []
             self.set_up_to_date(False)
         if self.synchronizer:
             self.synchronizer.add(address)
diff --git a/electrum/json_db.py b/electrum/json_db.py
index 84b3d6bdf..b6015fb40 100644
--- a/electrum/json_db.py
+++ b/electrum/json_db.py
@@ -115,9 +115,6 @@ class JsonDB(PrintError):
             return True
         return False
 
-    def commit(self):
-        pass
-
     @locked
     def dump(self):
         return json.dumps(self.data, indent=4, sort_keys=True, cls=JsonDBJsonEncoder)
diff --git a/electrum/sqlite_db.py b/electrum/sqlite_db.py
new file mode 100644
index 000000000..42097d3b1
--- /dev/null
+++ b/electrum/sqlite_db.py
@@ -0,0 +1,325 @@
+import os
+import sys
+import json
+from collections import defaultdict
+from operator import itemgetter
+import concurrent
+import threading
+import queue
+import traceback
+
+from sqlalchemy import create_engine, Column, ForeignKey, Integer, String, DateTime, Boolean
+from sqlalchemy.pool import StaticPool
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.orm.query import Query
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.sql import not_, or_
+from sqlalchemy.orm import scoped_session
+
+from .util import PrintError, standardize_path, TxMinedInfo
+from . import transaction
+
+Base = declarative_base()
+session_factory = sessionmaker()
+
+
+
+class Misc(Base):
+    __tablename__ = 'misc'
+    key  = Column(String(66), primary_key=True, sqlite_on_conflict_primary_key='REPLACE')
+    value = Column(String())
+
+class Txi(Base):
+    __tablename__ = 'txi'
+    id = Column(Integer, primary_key=True)
+    txid = Column(String())
+    address = Column(String())
+    ser = Column(String())
+    v = Column(Integer())
+
+class Txo(Base):
+    __tablename__ = 'txo'
+    id = Column(Integer, primary_key=True)
+    txid = Column(String())
+    address = Column(String())
+    n = Column(Integer())
+    v = Column(Integer())
+    is_coinbase = Column(Boolean())
+
+class Transaction(Base):
+    __tablename__ = 'transaction'
+    txid = Column(String(66), primary_key=True, sqlite_on_conflict_primary_key='REPLACE')
+    raw = Column(String())
+
+class Spent(Base):
+    __tablename__ = 'spent_outpoints'
+    id = Column(Integer, primary_key=True)
+    prev_txid = Column(String(66))
+    prev_n = Column(Integer())
+    ser = Column(String())
+
+class ImportedAddress(Base):
+    __tablename__ = 'imported_addresses'
+    id = Column(Integer, primary_key=True)
+    address = Column(String(66))
+
+class ReceivingAddress(Base):
+    __tablename__ = 'receiving_addresses'
+    id = Column(Integer, primary_key=True)
+    address = Column(String(66))
+
+class ChangeAddress(Base):
+    __tablename__ = 'change_addresses'
+    id = Column(Integer, primary_key=True)
+    address = Column(String(66))
+
+class AddressHistory(Base):
+    __tablename__ = 'address_history'
+    id = Column(Integer, primary_key=True)
+    address = Column(String(66))
+    txid = Column(String(66))
+    height = Column(Integer)
+
+class Keystore(Base):
+    __tablename__ = 'keystore'
+    name = Column(String(66), primary_key=True, sqlite_on_conflict_primary_key='REPLACE')
+    type = Column(String(10))
+    pw_hash_version = Column(Integer())
+    seed = Column(String())
+    xpub = Column(String())
+    xprv = Column(String())
+
+class VerifiedTx(Base):
+    __tablename__ = 'verified_tx'
+    txid = Column(String(), primary_key=True, sqlite_on_conflict_primary_key='REPLACE')
+    height = Column(Integer)
+    timestamp = Column(Integer)
+    txpos = Column(Integer)
+    header_hash = Column(String())
+
+    
+class SqliteDB(PrintError):
+
+    def __init__(self, raw, manual_upgrades=False):
+        # create db file in memory
+        self.tmp_path = '/dev/shm/xx'
+        self._modified = True
+        with open(self.tmp_path, 'wb') as f:
+            f.write(raw)
+        self.exists = bool(raw)
+        self.requests = queue.Queue()
+        threading.Thread(target=self.sql_thread, daemon=True).start()
+
+    def sql_thread(self):
+        self.engine = create_engine('sqlite:///' + self.tmp_path, pool_reset_on_return=None, poolclass=StaticPool)#, echo=True)
+        self.DBSession = scoped_session(session_factory)
+        self.DBSession.configure(bind=self.engine, autoflush=False)
+        self.DBSession.remove()
+        if not self.exists:
+            Base.metadata.create_all(self.engine)
+        while True:
+            future, func, args, kwargs = self.requests.get()
+            try:
+                result = func(self, *args, **kwargs)
+            except BaseException as e:
+                future.set_exception(e)
+                continue
+            future.set_result(result)
+
+    def sql(func):
+        def wrapper(self, *args, **kwargs):
+            f = concurrent.futures.Future()
+            self.requests.put((f, func, args, kwargs))
+            return f.result(timeout=3)
+        return wrapper
+
+    def requires_split(self):
+        return False
+
+    def requires_upgrade(self):
+        return False
+
+    def set_modified(self, b):
+        self._modified = b
+
+    def modified(self):
+        return self._modified
+
+    def dump(self):
+        with open(self.tmp_path, 'rb') as f:
+            return f.read()
+
+    def load_addresses(self, x):
+        pass
+
+    @sql
+    def put(self, key, v):
+        if key == 'keystore':
+            k = Keystore(name=key, type=v['type'], pw_hash_version=v['pw_hash_version'], seed=v.get('seed'), xpub=v.get('xpub'), xprv=v.get('xprv'))
+        else:
+            k = Misc(key=key, value=json.dumps(v))
+        self.DBSession.add(k)
+        self.DBSession.commit()
+
+    @sql
+    def get(self, key, default=None):
+        if key == 'keystore':
+            r = self.DBSession.query(Keystore).filter(Keystore.name == key).one_or_none()
+            if r:
+                r = {'type':r.type, 'pw_hash_version':r.pw_hash_version, 'seed':r.seed, 'xpub':r.xpub, 'xprv':r.xprv}
+        else:
+            r = self.DBSession.query(Misc).filter(Misc.key == key).one_or_none()
+            if r:
+                r = json.loads(r.value)
+        return r or default
+
+    @sql
+    def add_receiving_address(self, address):
+        self.DBSession.add(ReceivingAddress(address=address))
+        self.DBSession.commit()
+
+    @sql
+    def add_change_address(self, address):
+        self.DBSession.add(ChangeAddress(address=address))
+        self.DBSession.commit()
+
+    @sql
+    def get_receiving_addresses(self):
+        return list(map(itemgetter(0), self.DBSession.query(ReceivingAddress.address).all()))
+
+    @sql
+    def get_change_addresses(self):
+        return list(map(itemgetter(0), self.DBSession.query(ChangeAddress.address).all()))
+
+    @sql
+    def num_receiving_addresses(self):
+        return self.DBSession.query(ReceivingAddress).count()
+
+    @sql
+    def num_change_addresses(self):
+        return self.DBSession.query(ChangeAddress).count()
+
+    @sql
+    def get_address_index(self, address):
+        r = self.DBSession.query(ReceivingAddress).filter(ReceivingAddress.address==address).one_or_none()
+        if r:
+            return False, r.id - 1
+        r = self.DBSession.query(ChangeAddress).filter(ChangeAddress.address==address).one_or_none()
+        if r:
+            return True, r.id - 1
+        r = self.DBSession.query(ImportedAddress).filter(ImportedAddress.address==address).one_or_none()
+        if r:
+            return r.pubkey
+
+    @sql
+    def add_txi_addr(self, txid, address, ser, v):
+        if self.DBSession.query(Txi).filter(Txi.txid==txid, Txi.address==address, Txi.ser==ser, Txi.v==v).one_or_none():
+            return
+        self.DBSession.add(Txi(txid=txid, address=address, ser=ser, v=v))
+        self.DBSession.commit()
+
+    @sql
+    def add_txo_addr(self, txid, address, n, v, is_coinbase):
+        if self.DBSession.query(Txo).filter(Txo.txid==txid, Txo.address==address, Txo.n==n, Txo.v==v, Txo.is_coinbase==is_coinbase).one_or_none():
+            return
+        self.DBSession.add(Txo(txid=txid, address=address, n=n, v=v, is_coinbase=is_coinbase))
+        self.DBSession.commit()
+
+    @sql
+    def get_txi(self, txid):
+        return set(map(itemgetter(0), self.DBSession.query(Txi.address).filter(Txi.txid==txid).all()))
+
+    @sql
+    def get_txo(self, txid):
+        return set(map(itemgetter(0), self.DBSession.query(Txo.address).filter(Txo.txid==txid).all()))
+
+    @sql
+    def get_txi_addr(self, txid, address):
+        return [(r.ser, r.v) for r in self.DBSession.query(Txi).filter(Txi.txid==txid, Txi.address==address).all()]
+
+    @sql
+    def get_txo_addr(self, txid, address):
+        return [(r.n, r.v, r.is_coinbase) for r in self.DBSession.query(Txo).filter(Txo.txid==txid, Txo.address==address).all()]
+
+    @sql
+    def list_txi(self):
+        return set(map(itemgetter(0), self.DBSession.query(Txi.txid).all()))
+
+    @sql
+    def list_txo(self):
+        return set(map(itemgetter(0), self.DBSession.query(Txo.txid).all()))
+
+    @sql
+    def get_history(self):
+        return set(map(itemgetter(0), self.DBSession.query(AddressHistory.address).all()))
+
+    @sql
+    def get_addr_history(self, address):
+        return [(x.txid, x.height) for x in self.DBSession.query(AddressHistory).filter(AddressHistory.address==address).all()]
+
+    @sql
+    def set_addr_history(self, address, hist):
+        for txid, height in hist:
+            self.DBSession.add(AddressHistory(address=address, txid=txid, height=height))
+        self.DBSession.commit()
+
+    @sql
+    def is_in_verified_tx(self, txid):
+        return bool(self.DBSession.query(VerifiedTx).filter(VerifiedTx.txid==txid).one_or_none())
+
+    @sql
+    def add_verified_tx(self, txid, info):
+        self.DBSession.add(VerifiedTx(txid=txid, height=info.height, timestamp=info.timestamp, txpos=info.txpos, header_hash=info.header_hash))
+        self.DBSession.commit()
+
+    @sql
+    def get_verified_tx(self, txid):
+        r = self.DBSession.query(VerifiedTx).filter(VerifiedTx.txid==txid).one_or_none()
+        if not r:
+            return
+        return TxMinedInfo(height=r.height,
+                           conf=None,
+                           timestamp=r.timestamp,
+                           txpos=r.txpos,
+                           header_hash=r.header_hash)
+
+    @sql
+    def remove_verified_tx(self, txid):
+        v = self.DBSession.query(VerifiedTx).filter(VerifiedTx.txid==txid).one_or_none()
+        self.DBSession.delete(v)
+        self.DBSession.commit()
+
+    @sql
+    def get_spent_outpoints(self, prev_txid):
+        return [r.prev_n for r in self.DBSession.query(Spent).filter(Spent.prev_txid==prev_txid).all()]
+
+    @sql
+    def get_spent_outpoint(self, prev_txid, prev_n):
+        r = self.DBSession.query(Spent).filter(Spent.prev_txid==prev_txid, Spent.prev_n==prev_n).one_or_none()
+        return r.ser if r else None
+
+    @sql
+    def set_spent_outpoint(self, prev_txid, prev_n, ser):
+        r = self.DBSession.query(Spent).filter(Spent.prev_txid==prev_txid, Spent.prev_n==prev_n).one_or_none()
+        if r:
+            return
+        self.DBSession.add(Spent(prev_txid=prev_txid, prev_n=prev_n, ser=ser))
+        self.DBSession.commit()
+
+    @sql
+    def get_transaction(self, txid):
+        r = self.DBSession.query(Transaction).filter(Transaction.txid==txid).one_or_none()
+        return transaction.Transaction(r.raw) if r else None
+
+    @sql
+    def add_transaction(self, txid, tx):
+        self.DBSession.add(Transaction(txid=txid, raw=str(tx)))
+        self.DBSession.commit()
+
+    @sql
+    def update_tx_fees(self, tx_fees):
+        pass
+
+    @sql
+    def get_tx_fee(self, tx_hash):
+        pass
diff --git a/electrum/storage.py b/electrum/storage.py
index 9aef8a119..161068c39 100644
--- a/electrum/storage.py
+++ b/electrum/storage.py
@@ -33,6 +33,7 @@ from . import ecc
 from .util import PrintError, profiler, InvalidPassword, WalletFileException, bfh, standardize_path
 from .plugin import run_hook, plugin_loaders
 
+from .sqlite_db import SqliteDB
 from .json_db import JsonDB
 
 
@@ -48,16 +49,15 @@ STO_EV_PLAINTEXT, STO_EV_USER_PW, STO_EV_XPUB_PW = range(0, 3)
 
 class WalletStorage(PrintError):
 
-    def __init__(self, path, *, manual_upgrades=False):
+    def __init__(self, path, *, manual_upgrades=False, use_sql=False):
         self.lock = threading.RLock()
         self.path = standardize_path(path)
         self._file_exists = self.path and os.path.exists(self.path)
-
-        DB_Class = JsonDB
+        DB_Class = SqliteDB# if use_sql else JsonDB
         self.print_error("wallet path", self.path)
         self.pubkey = None
         if self.file_exists():
-            with open(self.path, "r", encoding='utf-8') as f:
+            with open(self.path, "rb") as f:
                 self.raw = f.read()
             self._encryption_version = self._init_encryption_version()
             if not self.is_encrypted():
@@ -66,7 +66,7 @@ class WalletStorage(PrintError):
         else:
             self._encryption_version = STO_EV_PLAINTEXT
             # avoid new wallets getting 'upgraded'
-            self.db = DB_Class('', manual_upgrades=False)
+            self.db = DB_Class(b'', manual_upgrades=False)
 
 
     def load_plugins(self):
@@ -91,10 +91,10 @@ class WalletStorage(PrintError):
             return
         if not self.db.modified():
             return
-        self.db.commit()
+
         s = self.encrypt_before_writing(self.db.dump())
         temp_path = "%s.tmp.%s" % (self.path, os.getpid())
-        with open(temp_path, "w", encoding='utf-8') as f:
+        with open(temp_path, "wb") as f:
             f.write(s)
             f.flush()
             os.fsync(f.fileno())
@@ -219,8 +219,8 @@ class WalletStorage(PrintError):
         self.db.set_modified(True)
 
     def requires_upgrade(self):
-        if not self.is_past_initial_decryption():
-            raise Exception("storage not yet decrypted!")
+        #if not self.is_past_initial_decryption():
+        #    raise Exception("storage not yet decrypted!")
         return self.db.requires_upgrade()
 
     def upgrade(self):