diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,2 +1,3 @@
 swh.core[http] >= 0.3
 swh.model >= 0.0.27
+#swh.prefecthash
diff --git a/requirements-test.txt b/requirements-test.txt
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -5,3 +5,5 @@
 requests_toolbelt
 types-pyyaml
 types-requests
+pytest-postgresql < 4.0.0  # version 4.0 depends on psycopg 3. https://github.com/ClearcodeHQ/pytest-postgresql/blob/main/CHANGES.rst#400
+
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,7 @@
 aiohttp >= 3
 click
 requests
+psycopg2
 
 # optional dependencies
 # apache-libcloud
diff --git a/swh/objstorage/backends/winery/__init__.py b/swh/objstorage/backends/winery/__init__.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/backends/winery/__init__.py
@@ -0,0 +1 @@
+from .objstorage import WineryObjStorage  # noqa: F401
diff --git a/swh/objstorage/backends/winery/database.py b/swh/objstorage/backends/winery/database.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/backends/winery/database.py
@@ -0,0 +1,75 @@
+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import logging
+import time
+
+import psycopg2
+
+LOGGER = logging.getLogger(__name__)
+LOGGER.setLevel(logging.ERROR)
+
+
+class Database:
+    def __init__(self, dsn):
+        self.dsn = dsn
+
+    def create_database(self, database):
+        db = psycopg2.connect(f"{self.dsn}/postgres")
+        db.autocommit = True
+        c = db.cursor()
+        c.execute(
+            f"SELECT datname FROM pg_catalog.pg_database WHERE datname = '{database}'"
+        )
+        if c.rowcount == 0:
+            c.execute(f"CREATE DATABASE {database}")
+        c.close()
+
+    def drop_database(self, database):
+        db = psycopg2.connect(f"{self.dsn}/postgres")
+        # https://wiki.postgresql.org/wiki/Psycopg2_Tutorial
+        # If you want to drop the database you would need to
+        # change the isolation level of the database.
+        db.set_isolation_level(0)
+        db.autocommit = True
+        c = db.cursor()
+        #
+        # Dropping the database may fail because the server takes time
+        # to notice a connection was dropped and/or a named cursor is
+        # in the process of being deleted. It can happen here or even
+        # when deleting all database with the psql cli
+        # and there are no bench process active.
+        #
+        # ERROR: database "i606428a5a6274d1ab09eecc4d019fef7" is being
+        # accessed by other users DETAIL: There is 1 other session
+        # using the database.
+        #
+        # See:
+        # https://stackoverflow.com/questions/5108876/kill-a-postgresql-session-connection
+        #
+        # https://www.postgresql.org/docs/current/sql-dropdatabase.html
+        #
+        # WITH (FORCE) added in postgresql 13 but may also fail because the
+        # named cursor may not be handled as a client.
+        #
+        for i in range(60):
+            try:
+                c.execute(f"DROP DATABASE IF EXISTS {database}")
+                break
+            except psycopg2.errors.ObjectInUse:
+                LOGGER.warning(f"{database} database drop fails, waiting")
+                time.sleep(10)
+                continue
+            raise Exception("database drop fails {database}")
+        c.close()
+
+    def list_databases(self):
+        db = psycopg2.connect(f"{self.dsn}/postgres")
+        with db.cursor() as c:
+            c.execute(
+                "SELECT datname FROM pg_database "
+                "WHERE datistemplate = false and datname != 'postgres'"
+            )
+            return [r[0] for r in c.fetchall()]
diff --git a/swh/objstorage/backends/winery/objstorage.py b/swh/objstorage/backends/winery/objstorage.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/backends/winery/objstorage.py
@@ -0,0 +1,96 @@
+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import concurrent.futures
+import logging
+
+from swh.objstorage import exc
+from swh.objstorage.objstorage import ObjStorage, compute_hash
+
+from .rwshard import RWShard
+from .sharedbase import SharedBase
+
+LOGGER = logging.getLogger(__name__)
+LOGGER.setLevel(logging.ERROR)
+
+
+def pack(shard, **kwargs):
+    return Packer(shard, **kwargs).run()
+
+
+class Packer:
+    def __init__(self, shard, **kwargs):
+        self.args = kwargs
+        self.base = SharedBase(**self.args)
+        self.shard = RWShard(shard, **self.args)
+
+    def run(self):
+        return True
+
+
+class WineryObjStorage(ObjStorage):
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self.args = kwargs
+        self.executor = concurrent.futures.ProcessPoolExecutor(max_workers=1)
+        self.packers = []
+        self.init()
+
+    def init(self):
+        self.base = SharedBase(**self.args)
+        self.shard = RWShard(self.base.whoami, **self.args)
+
+    def check_config(self, *, check_write):
+        return True
+
+    def __contains__(self, obj_id):
+        return self.base.contains(obj_id)
+
+    def add(self, content, obj_id=None, check_presence=True):
+        if obj_id is None:
+            obj_id = compute_hash(content)
+
+        if check_presence and obj_id in self:
+            return obj_id
+
+        shard = self.base.add_phase_1(obj_id)
+        if shard != self.base.id:
+            #  this object is the responsibility of another shard
+            return obj_id
+
+        self.shard.add(obj_id, content)
+        self.base.add_phase_2(obj_id)
+
+        if self.shard.is_full():
+            self.pack()
+
+        return obj_id
+
+    def get(self, obj_id):
+        shard_info = self.base.get(obj_id)
+        if shard_info is None:
+            raise exc.ObjNotFoundError(obj_id)
+        name, readonly = shard_info
+        if readonly:
+            pass  # ROShard
+        else:
+            shard = RWShard(name, **self.args)
+            content = shard.get(obj_id)
+        if content is None:
+            raise exc.ObjNotFoundError(obj_id)
+        return content
+
+    def check(self, obj_id):
+        # load all shards readonly == NULL and not locked (i.e. packer
+        # was interrupted for whatever reason) run pack for each of them
+        pass
+
+    def delete(self, obj_id):
+        raise PermissionError("Delete is not allowed.")
+
+    def pack(self):
+        self.base.shard_packing_starts()
+        self.packers.append(self.executor.submit(pack, self.shard.name, **self.args))
+        self.init()
diff --git a/swh/objstorage/backends/winery/rwshard.py b/swh/objstorage/backends/winery/rwshard.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/backends/winery/rwshard.py
@@ -0,0 +1,68 @@
+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+
+import psycopg2
+
+from .database import Database
+
+
+class RWShard(Database):
+    def __init__(self, name, **kwargs):
+        super().__init__(kwargs["shard_dsn"])
+        self._name = name
+        self.create_database(self.name)
+        self.db = self.create_table(f"{self.dsn}/{self.name}")
+        self.size = self.total_size()
+        self.limit = kwargs["shard_max_size"]
+
+    @property
+    def name(self):
+        return self._name
+
+    def is_full(self):
+        return self.size > self.limit
+
+    def create_table(self, dsn):
+        db = psycopg2.connect(dsn)
+        db.autocommit = True
+        c = db.cursor()
+        c.execute(
+            "CREATE TABLE IF NOT EXISTS objects("
+            "key BYTEA PRIMARY KEY, "
+            "content BYTEA "
+            ")"
+        )
+        c.close()
+        return db
+
+    def total_size(self):
+        with self.db.cursor() as c:
+            c.execute("SELECT SUM(LENGTH(content)) FROM objects")
+            size = c.fetchone()[0]
+            if size is None:
+                return 0
+            else:
+                return int(size)
+
+    def add(self, obj_id, content):
+        try:
+            with self.db.cursor() as c:
+                c.execute(
+                    "INSERT INTO objects (key, content) VALUES (%s, %s)",
+                    (obj_id, content),
+                )
+            self.db.commit()
+            self.size += len(content)
+        except psycopg2.errors.UniqueViolation:
+            pass
+
+    def get(self, obj_id):
+        with self.db.cursor() as c:
+            c.execute("SELECT content FROM objects WHERE key = %s", (obj_id,))
+            if c.rowcount == 0:
+                return None
+            else:
+                return c.fetchone()[0].tobytes()
diff --git a/swh/objstorage/backends/winery/sharedbase.py b/swh/objstorage/backends/winery/sharedbase.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/backends/winery/sharedbase.py
@@ -0,0 +1,150 @@
+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import uuid
+
+import psycopg2
+
+from .database import Database
+
+
+class SharedBase(Database):
+    def __init__(self, **kwargs):
+        super().__init__(kwargs["base_dsn"])
+        database = "sharedbase"
+        self.create_database(database)
+        self.db = self.create_table(f"{self.dsn}/{database}")
+        self._whoami = None
+
+    def create_table(self, dsn):
+        db = psycopg2.connect(dsn)
+        db.autocommit = True
+        c = db.cursor()
+        c.execute(
+            "CREATE TABLE IF NOT EXISTS shards("
+            "id SERIAL PRIMARY KEY, "
+            "readonly BOOLEAN DEFAULT FALSE, "
+            "name CHAR(32) NOT NULL "
+            ")"
+        )
+        c.execute(
+            "CREATE TABLE IF NOT EXISTS signature2shard("
+            "signature BYTEA PRIMARY KEY, "
+            "inflight BOOLEAN DEFAULT TRUE NOT NULL, "
+            "shard INTEGER NOT NULL"
+            ")"
+        )
+        c.close()
+        return db
+
+    @property
+    def whoami(self):
+        self.set_whoami()
+        return self._whoami
+
+    @property
+    def id(self):
+        self.set_whoami()
+        return self._whoami_id
+
+    def set_whoami(self):
+        if self._whoami is not None:
+            return
+
+        while True:
+            self._whoami, self._whoami_id = self.lock_a_shard()
+            if self._whoami is not None:
+                return self._whoami
+            self.create_shard()
+
+    def lock_a_shard(self):
+        with self.db.cursor() as c:
+            c.execute(
+                "SELECT name FROM shards WHERE readonly = FALSE "
+                "LIMIT 1 FOR UPDATE SKIP LOCKED"
+            )
+            if c.rowcount == 0:
+                return None, None
+            name = c.fetchone()[0]
+        return self.lock_shard(name)
+
+    def lock_shard(self, name):
+        self.whoami_lock = self.db.cursor()
+        try:
+            self.whoami_lock.execute(
+                "SELECT name, id FROM shards "
+                "WHERE readonly = FALSE AND name = %s FOR UPDATE NOWAIT",
+                (name,),
+            )
+            return self.whoami_lock.fetchone()
+        except Exception:
+            return None
+
+    def create_shard(self):
+        name = uuid.uuid4().hex
+        name = "i" + name[1:]  # ensure the first character is not a number
+        with self.db.cursor() as c:
+            c.execute("INSERT INTO shards (name, readonly) VALUES (%s, FALSE)", (name,))
+        self.db.commit()
+
+    def shard_packing_starts(self):
+        with self.db.cursor() as c:
+            c.execute(
+                "UPDATE shards SET readonly = NULL WHERE name = %s", (self.whoami,)
+            )
+
+    def shard_packing_ends(self):
+        with self.db.cursor() as c:
+            c.execute(
+                "UPDATE shards SET readonly = TRUE WHERE name = %s", (self.whoami,)
+            )
+
+    def get_shard_info(self, id):
+        with self.db.cursor() as c:
+            c.execute("SELECT name, readonly FROM shards WHERE id = %s", (id,))
+            if c.rowcount == 0:
+                return None
+            else:
+                return c.fetchone()
+
+    def contains(self, obj_id):
+        with self.db.cursor() as c:
+            c.execute(
+                "SELECT shard FROM signature2shard WHERE "
+                "signature = %s AND inflight = FALSE",
+                (obj_id,),
+            )
+            if c.rowcount == 0:
+                return None
+            else:
+                return c.fetchone()[0]
+
+    def get(self, obj_id):
+        id = self.contains(obj_id)
+        if id is None:
+            return None
+        return self.get_shard_info(id)
+
+    def add_phase_1(self, obj_id):
+        try:
+            with self.db.cursor() as c:
+                c.execute(
+                    "INSERT INTO signature2shard (signature, shard, inflight) "
+                    "VALUES (%s, %s, TRUE)",
+                    (obj_id, self.id),
+                )
+            self.db.commit()
+            return self.id
+        except psycopg2.errors.UniqueViolation:
+            return self.contains(obj_id)
+
+    def add_phase_2(self, obj_id):
+        with self.db.cursor() as c:
+            c.execute(
+                "UPDATE signature2shard SET inflight = FALSE "
+                "WHERE signature = %s AND shard = %s",
+                (obj_id, self.id),
+            )
+        self.db.commit()
diff --git a/swh/objstorage/factory.py b/swh/objstorage/factory.py
--- a/swh/objstorage/factory.py
+++ b/swh/objstorage/factory.py
@@ -13,6 +13,7 @@
 from swh.objstorage.backends.noop import NoopObjStorage
 from swh.objstorage.backends.pathslicing import PathSlicingObjStorage
 from swh.objstorage.backends.seaweedfs import SeaweedFilerObjStorage
+from swh.objstorage.backends.winery import WineryObjStorage
 from swh.objstorage.multiplexer import MultiplexerObjStorage, StripingObjStorage
 from swh.objstorage.multiplexer.filter import add_filters
 from swh.objstorage.objstorage import ID_HASH_LENGTH, ObjStorage  # noqa
@@ -27,6 +28,7 @@
     "seaweedfs": SeaweedFilerObjStorage,
     "random": RandomGeneratorObjStorage,
     "http": HTTPReadOnlyObjStorage,
+    "winery": WineryObjStorage,
     "noop": NoopObjStorage,
 }
 
diff --git a/swh/objstorage/tests/test_objstorage_winery.py b/swh/objstorage/tests/test_objstorage_winery.py
new file mode 100644
--- /dev/null
+++ b/swh/objstorage/tests/test_objstorage_winery.py
@@ -0,0 +1,78 @@
+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import concurrent.futures
+
+import pytest
+
+from swh.objstorage import exc
+from swh.objstorage.backends.winery.database import Database
+from swh.objstorage.factory import get_objstorage
+
+
+@pytest.fixture
+def dsn(postgresql):
+    dsn = (
+        f"postgres://{postgresql.info.user}"
+        f":@{postgresql.info.host}:{postgresql.info.port}"
+    )
+    yield dsn
+    # pytest-postgresql will not remove databases that it did not create
+    d = Database(dsn)
+    for database in d.list_databases():
+        if database != postgresql.info.dbname and database != "tests_tmpl":
+            d.drop_database(database)
+
+
+def test_winery_sharedbase(dsn):
+    base = get_objstorage(
+        cls="winery", base_dsn=dsn, shard_dsn=dsn, shard_max_size=1
+    ).base
+    shard1 = base.whoami
+    assert shard1 is not None
+    assert shard1 == base.whoami
+
+    id1 = base.id
+    assert id1 is not None
+    assert id1 == base.id
+
+
+def test_winery_add_get(dsn):
+    winery = get_objstorage(
+        cls="winery", base_dsn=dsn, shard_dsn=dsn, shard_max_size=1024
+    )
+    shard = winery.base.whoami
+    content = b"SOMETHING"
+    obj_id = winery.add(content=content)
+    assert obj_id.hex() == "0c8c841f7d9fd4874d841506d3ffc16808b1d579"
+    assert winery.add(content=content, obj_id=obj_id) == obj_id
+    assert winery.add(content=content, obj_id=obj_id, check_presence=False) == obj_id
+    assert winery.base.whoami == shard
+    assert winery.get(obj_id) == content
+    with pytest.raises(exc.ObjNotFoundError):
+        winery.get(b"unknown")
+
+
+def test_winery_add_and_pack(dsn):
+    winery = get_objstorage(cls="winery", base_dsn=dsn, shard_dsn=dsn, shard_max_size=1)
+    shard = winery.base.whoami
+    content = b"SOMETHING"
+    obj_id = winery.add(content=content)
+    assert obj_id.hex() == "0c8c841f7d9fd4874d841506d3ffc16808b1d579"
+    assert winery.base.whoami != shard
+    assert len(winery.packers) == 1
+    done, not_done = concurrent.futures.wait(winery.packers)
+    assert len(not_done) == 0
+    assert len(done) == 1
+    packer = list(done)[0]
+    assert packer.exception(timeout=0) is None
+    assert packer.result() is True
+    winery.executor.shutdown()
+
+
+def test_winery_delete(dsn):
+    winery = get_objstorage(cls="winery", base_dsn=dsn, shard_dsn=dsn, shard_max_size=1)
+    with pytest.raises(PermissionError):
+        winery.delete(None)
diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -10,7 +10,7 @@
 commands =
   pytest --cov={envsitepackagesdir}/swh/objstorage \
          {envsitepackagesdir}/swh/objstorage \
-         --cov-branch {posargs}
+         --cov-branch --cov-report term-missing {posargs}
 
 [testenv:black]
 skip_install = true