diff --git a/chainsyncer/backend.py b/chainsyncer/backend.py
index 3380bfc..5953ff2 100644
--- a/chainsyncer/backend.py
+++ b/chainsyncer/backend.py
@@ -7,6 +7,7 @@ from chainlib.chain import ChainSpec
 
 # local imports
 from chainsyncer.db.models.sync import BlockchainSync
+from chainsyncer.db.models.filter import BlockchainSyncFilter
 from chainsyncer.db.models.base import SessionBase
 
 logg = logging.getLogger()
@@ -23,6 +24,7 @@ class SyncerBackend:
     def __init__(self, chain_spec, object_id):
         self.db_session = None
         self.db_object = None
+        self.db_object_filter = None
         self.chain_spec = chain_spec
         self.object_id = object_id
         self.connect()
@@ -34,9 +36,17 @@ class SyncerBackend:
         """
         if self.db_session == None:
             self.db_session = SessionBase.create_session()
+
         q = self.db_session.query(BlockchainSync)
         q = q.filter(BlockchainSync.id==self.object_id)
         self.db_object = q.first()
+
+        if self.db_object != None:
+            qtwo = self.db_session.query(BlockchainSyncFilter)
+            qtwo = qtwo.join(BlockchainSync)
+            qtwo = qtwo.filter(BlockchainSync.id==self.db_object.id)
+            self.db_object_filter = qtwo.first()
+
         if self.db_object == None:
             raise ValueError('sync entry with id {} not found'.format(self.object_id))
 
@@ -44,6 +54,8 @@ class SyncerBackend:
     def disconnect(self):
         """Commits state of sync to backend.
         """
+        if self.db_object_filter != None:
+            self.db_session.add(self.db_object_filter)
         self.db_session.add(self.db_object)
         self.db_session.commit()
         self.db_session.close()
@@ -67,8 +79,9 @@ class SyncerBackend:
         """
         self.connect()
         pair = self.db_object.cursor()
+        filter_state = self.db_object_filter.filter()
         self.disconnect()
-        return pair
+        return (pair, filter_state,)
    
 
     def set(self, block_height, tx_height):
@@ -82,8 +95,9 @@ class SyncerBackend:
         """
         self.connect()
         pair = self.db_object.set(block_height, tx_height)
+        filter_state = self.db_object_filter.filter()
         self.disconnect()
-        return pair
+        return (pair, filter_state,)
 
 
     def start(self):
@@ -94,8 +108,9 @@ class SyncerBackend:
         """
         self.connect()
         pair = self.db_object.start()
+        filter_state = self.db_object_filter.start()
         self.disconnect()
-        return pair
+        return (pair, filter_state,)
 
     
     def target(self):
@@ -106,12 +121,13 @@ class SyncerBackend:
         """
         self.connect()
         target = self.db_object.target()
+        filter_state = self.db_object_filter.target()
         self.disconnect()
-        return target
+        return (target, filter_target,)
 
 
     @staticmethod
-    def first(chain):
+    def first(chain_spec):
         """Returns the model object of the most recent syncer in backend.
 
         :param chain: Chain spec of chain that syncer is running for.
@@ -119,7 +135,12 @@ class SyncerBackend:
         :returns: Last syncer object 
         :rtype: cic_eth.db.models.BlockchainSync
         """
-        return BlockchainSync.first(chain)
+        #return BlockchainSync.first(str(chain_spec))
+        object_id = BlockchainSync.first(str(chain_spec))
+        if object_id == None:
+            return None
+        return SyncerBackend(chain_spec, object_id)
+
 
 
     @staticmethod
@@ -193,15 +214,30 @@ class SyncerBackend:
         """
         object_id = None
         session = SessionBase.create_session()
+
         o = BlockchainSync(str(chain_spec), block_height, 0, None)
         session.add(o)
-        session.commit()
+        session.flush()
         object_id = o.id
+
+        of = BlockchainSyncFilter(o)
+        session.add(of)
+        session.commit()
+
         session.close()
 
         return SyncerBackend(chain_spec, object_id)
 
 
+    def register_filter(self, name):
+        self.connect()
+        if self.db_object_filter == None:
+            self.db_object_filter = BlockchainSyncFilter(self.db_object)
+        self.db_object_filter.add(name)
+        self.db_session.add(self.db_object_filter)
+        self.disconnect()
+
+
 class MemBackend:
 
     def __init__(self, chain_spec, object_id):
@@ -209,6 +245,7 @@ class MemBackend:
         self.chain_spec = chain_spec
         self.block_height = 0
         self.tx_height = 0
+        self.flags = 0
         self.db_session = None
 
 
diff --git a/chainsyncer/db/models/base.py b/chainsyncer/db/models/base.py
index 153906a..db570df 100644
--- a/chainsyncer/db/models/base.py
+++ b/chainsyncer/db/models/base.py
@@ -1,8 +1,18 @@
+# stanard imports
+import logging
+
 # third-party imports
 from sqlalchemy import Column, Integer
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import (
+        StaticPool,
+        QueuePool,
+        AssertionPool,
+        )
+
+logg = logging.getLogger()
 
 Model = declarative_base(name='Model')
 
@@ -21,7 +31,11 @@ class SessionBase(Model):
     transactional = True
     """Whether the database backend supports query transactions. Should be explicitly set by initialization code"""
     poolable = True
-    """Whether the database backend supports query transactions. Should be explicitly set by initialization code"""
+    """Whether the database backend supports connection pools. Should be explicitly set by initialization code"""
+    procedural = True
+    """Whether the database backend supports stored procedures"""
+    localsessions = {}
+    """Contains dictionary of sessions initiated by db model components"""
 
 
     @staticmethod
@@ -40,7 +54,7 @@ class SessionBase(Model):
 
 
     @staticmethod
-    def connect(dsn, debug=False):
+    def connect(dsn, pool_size=8, debug=False):
         """Create new database connection engine and connect to database backend.
 
         :param dsn: DSN string defining connection.
@@ -48,14 +62,28 @@ class SessionBase(Model):
         """
         e = None
         if SessionBase.poolable:
-            e = create_engine(
-                    dsn,
-                    max_overflow=50,
-                    pool_pre_ping=True,
-                    pool_size=20,
-                    pool_recycle=10,
-                    echo=debug,
-                )
+            poolclass = QueuePool
+            if pool_size > 1:
+                e = create_engine(
+                        dsn,
+                        max_overflow=pool_size*3,
+                        pool_pre_ping=True,
+                        pool_size=pool_size,
+                        pool_recycle=60,
+                        poolclass=poolclass,
+                        echo=debug,
+                    )
+            else:
+                if debug:
+                    poolclass = AssertionPool
+                else:
+                    poolclass = StaticPool
+
+                e = create_engine(
+                        dsn,
+                        poolclass=poolclass,
+                        echo=debug,
+                    )
         else:
             e = create_engine(
                     dsn,
@@ -71,3 +99,24 @@ class SessionBase(Model):
         """
         SessionBase.engine.dispose()
         SessionBase.engine = None
+
+
+    @staticmethod
+    def bind_session(session=None):
+        localsession = session
+        if localsession == None:
+            localsession = SessionBase.create_session()
+            localsession_key = str(id(localsession))
+            logg.debug('creating new session {}'.format(localsession_key))
+            SessionBase.localsessions[localsession_key] = localsession
+        return localsession
+
+
+    @staticmethod
+    def release_session(session=None):
+        session.flush()
+        session_key = str(id(session))
+        if SessionBase.localsessions.get(session_key) != None:
+            logg.debug('destroying session {}'.format(session_key))
+            session.commit()
+            session.close()
diff --git a/chainsyncer/db/models/filter.py b/chainsyncer/db/models/filter.py
index 89bd564..656ed62 100644
--- a/chainsyncer/db/models/filter.py
+++ b/chainsyncer/db/models/filter.py
@@ -1,40 +1,79 @@
 # standard imports
+import logging
 import hashlib
 
-# third-party imports
-from sqlalchemy import Column, String, Integer, BLOB
+# external imports
+from sqlalchemy import Column, String, Integer, BLOB, ForeignKey
 from sqlalchemy.ext.hybrid import hybrid_property, hybrid_method
 
 # local imports
 from .base import SessionBase
+from .sync import BlockchainSync
 
-
-zero_digest = '{:<064s'.format('0')
+zero_digest = bytearray(32)
+logg = logging.getLogger(__name__)
 
 
 class BlockchainSyncFilter(SessionBase):
 
     __tablename__ = 'chain_sync_filter'
 
-    chain_sync_id = Column(Integer, ForeignKey='chain_sync.id')
+    chain_sync_id = Column(Integer, ForeignKey('chain_sync.id'))
+    flags_start = Column(BLOB)
     flags = Column(BLOB)
-    digest = Column(String)
+    digest = Column(BLOB)
     count = Column(Integer)
 
-    @staticmethod
-    def set(self, names):
 
-
-    def __init__(self, names, chain_sync, digest=None):
-        if len(names) == 0:
-            digest = zero_digest
-        elif digest == None:
-            h = hashlib.new('sha256')
-            for n in names:
-                h.update(n.encode('utf-8') + b'\x00')
-            z = h.digest()
-            digest = z.hex()
+    def __init__(self, chain_sync, count=0, flags=None, digest=zero_digest):
         self.digest = digest
-        self.count = len(names)
-        self.flags = bytearray((len(names) -1 ) / 8 + 1)
+        self.count = count
+
+        if flags == None:
+            flags = bytearray(0)
+        self.flags_start = flags
+        self.flags = flags
+
         self.chain_sync_id = chain_sync.id
+
+
+    def add(self, name):
+        h = hashlib.new('sha256')
+        h.update(self.digest)
+        h.update(name.encode('utf-8'))
+        z = h.digest()
+
+        old_byte_count = int((self.count - 1) / 8 + 1)
+        new_byte_count = int((self.count) / 8 + 1)
+
+        logg.debug('old new {} {}'.format(old_byte_count, new_byte_count))
+        if old_byte_count != new_byte_count:
+            self.flags = bytearray(1) + self.flags
+        self.count += 1
+        self.digest = z
+
+
+    def start(self):
+        return self.flags_start
+
+
+    def cursor(self):
+        return self.flags_current
+
+
+    def clear(self):
+        self.flags = 0
+
+
+    def target(self):
+        n = 0
+        for i in range(self.count):
+            n |= 2 << i
+        return n
+
+
+    def set(self, n):
+        if self.flags & n > 0:
+            SessionBase.release_session(session)
+            raise AttributeError('Filter bit already set')
+        r.flags |= n
diff --git a/chainsyncer/db/models/sync.py b/chainsyncer/db/models/sync.py
index 6dab033..4f2f156 100644
--- a/chainsyncer/db/models/sync.py
+++ b/chainsyncer/db/models/sync.py
@@ -41,19 +41,23 @@ class BlockchainSync(SessionBase):
         :type chain: str
         :param session: Session to use. If not specified, a separate session will be created for this method only.
         :type session: SqlAlchemy Session
-        :returns: True if sync record found
-        :rtype: bool
+        :returns: Database primary key id of sync record
+        :rtype: number|None
         """
-        local_session = False
-        if session == None:
-            session = SessionBase.create_session()
-            local_session = True
+        session = SessionBase.bind_session(session)
+
         q = session.query(BlockchainSync.id)
         q = q.filter(BlockchainSync.blockchain==chain)
         o = q.first()
-        if local_session:
-            session.close()
-        return o == None
+
+        if o == None:
+            return None
+
+        sync_id = o.id
+
+        SessionBase.release_session(session)
+
+        return sync_id
 
 
     @staticmethod
@@ -165,4 +169,4 @@ class BlockchainSync(SessionBase):
         self.tx_cursor = tx_start
         self.block_target = block_target
         self.date_created = datetime.datetime.utcnow()
-        self.date_modified = datetime.datetime.utcnow()
+        self.date_updated = datetime.datetime.utcnow()
diff --git a/chainsyncer/filter.py b/chainsyncer/filter.py
index e488b8c..263bbe5 100644
--- a/chainsyncer/filter.py
+++ b/chainsyncer/filter.py
@@ -9,6 +9,7 @@ from .error import BackendError
 
 logg = logging.getLogger(__name__)
 
+
 class SyncFilter:
 
     def __init__(self, backend, safe=True):
@@ -32,11 +33,15 @@ class SyncFilter:
         except sqlalchemy.exc.TimeoutError as e:
             self.backend.disconnect()
             raise BackendError('database connection fail: {}'.format(e))
+        i = 0
         for f in self.filters:
+            i += 1
             logg.debug('applying filter {}'.format(str(f)))
             f.filter(conn, block, tx, self.backend.db_session)
+            self.backend.set_filter()
         self.backend.disconnect()
 
+
 class NoopFilter:
     
     def filter(self, conn, block, tx, db_session=None):
diff --git a/sql/sqlite/1.sql b/sql/sqlite/1.sql
index fa9f6fa..0f115d4 100644
--- a/sql/sqlite/1.sql
+++ b/sql/sqlite/1.sql
@@ -1,13 +1,11 @@
 CREATE TABLE IF NOT EXISTS chain_sync (
-	id serial primary key not null,
+	id integer primary key autoincrement,
 	blockchain varchar not null,
-	block_start int not null default 0,
-	tx_start int not null default 0,
-	block_cursor int not null default 0,
-	tx_cursor int not null default 0,
-	flags bytea not null,
-	num_flags int not null,
-	block_target int default null,
+	block_start integer not null default 0,
+	tx_start integer not null default 0,
+	block_cursor integer not null default 0,
+	tx_cursor integer not null default 0,
+	block_target integer default null,
 	date_created timestamp not null,
 	date_updated timestamp default null
 );
diff --git a/sql/sqlite/2.sql b/sql/sqlite/2.sql
index c43624e..9e42802 100644
--- a/sql/sqlite/2.sql
+++ b/sql/sqlite/2.sql
@@ -1,8 +1,9 @@
 CREATE TABLE IF NOT EXISTS chain_sync_filter (
-	id serial primary key not null,
-	chain_sync_id int not null,
+	id integer primary key autoincrement not null,
+	chain_sync_id integer not null,
 	flags bytea default null,
-	count int not null default 0,
+	flags_start bytea default null,
+	count integer not null default 0,
 	digest char(64) not null default '0000000000000000000000000000000000000000000000000000000000000000',
 	CONSTRAINT fk_chain_sync
 		FOREIGN KEY(chain_sync_id)
diff --git a/tests/base.py b/tests/base.py
index 6729eb9..2d0a99c 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -1,13 +1,21 @@
+# standard imports
+import logging
 import unittest
 import tempfile
 import os
 #import pysqlite
 
+# external imports
+from chainlib.chain import ChainSpec
+
+# local imports
 from chainsyncer.db import dsn_from_config
 from chainsyncer.db.models.base import SessionBase
 
 script_dir = os.path.realpath(os.path.dirname(__file__))
 
+logging.basicConfig(level=logging.DEBUG)
+
 
 class TestBase(unittest.TestCase):
 
@@ -23,7 +31,7 @@ class TestBase(unittest.TestCase):
         SessionBase.poolable = False
         SessionBase.transactional = False
         SessionBase.procedural = False
-        SessionBase.connect(dsn, debug=True)
+        SessionBase.connect(dsn, debug=False)
 
         f = open(os.path.join(script_dir, '..', 'sql', 'sqlite', '1.sql'), 'r')
         sql = f.read()
@@ -39,6 +47,8 @@ class TestBase(unittest.TestCase):
         conn = SessionBase.engine.connect()
         conn.execute(sql)
 
+        self.chain_spec = ChainSpec('evm', 'foo', 42, 'bar')
+
     def tearDown(self):
         SessionBase.disconnect()
         os.unlink(self.db_path)
diff --git a/tests/test_database.py b/tests/test_database.py
new file mode 100644
index 0000000..22f919b
--- /dev/null
+++ b/tests/test_database.py
@@ -0,0 +1,55 @@
+# standard imports
+import unittest
+
+# external imports
+from chainlib.chain import ChainSpec
+
+# local imports
+from chainsyncer.db.models.base import SessionBase
+from chainsyncer.db.models.filter import BlockchainSyncFilter
+from chainsyncer.backend import SyncerBackend
+
+# testutil imports
+from tests.base import TestBase
+
+class TestDatabase(TestBase):
+
+
+    def test_backend_live(self):
+        s = SyncerBackend.live(self.chain_spec, 42)
+        self.assertEqual(s.object_id, 1)
+        backend = SyncerBackend.first(self.chain_spec)
+        #SyncerBackend(self.chain_spec, sync_id)
+        self.assertEqual(backend.object_id, 1)
+
+        bogus_chain_spec = ChainSpec('bogus', 'foo', 13, 'baz')
+        sync_id = SyncerBackend.first(bogus_chain_spec)
+        self.assertIsNone(sync_id)
+
+
+    def test_backend_filter(self):
+        s = SyncerBackend.live(self.chain_spec, 42)
+
+        s.connect()
+        filter_id = s.db_object_filter.id
+        s.disconnect()
+
+        session = SessionBase.create_session()
+        o = session.query(BlockchainSyncFilter).get(filter_id)
+        self.assertEqual(len(o.flags), 0)
+        session.close()
+
+        for i in range(9):
+            s.register_filter(str(i))
+
+        s.connect()
+        filter_id = s.db_object_filter.id
+        s.disconnect()
+
+        session = SessionBase.create_session()
+        o = session.query(BlockchainSyncFilter).get(filter_id)
+        self.assertEqual(len(o.flags), 2)
+        session.close()
+
+if __name__ == '__main__':
+    unittest.main()