diff --git a/swh/core/db/__init__.py b/swh/core/db/__init__.py
--- a/swh/core/db/__init__.py
+++ b/swh/core/db/__init__.py
@@ -10,12 +10,13 @@
 import os
 import sys
 import threading
-from typing import Any, Callable, Iterable, Mapping, Optional
+from typing import Any, Callable, Iterable, Iterator, Mapping, Optional, Type, TypeVar
 
 from contextlib import contextmanager
 
 import psycopg2
 import psycopg2.extras
+import psycopg2.pool
 
 
 logger = logging.getLogger(__name__)
@@ -112,6 +113,9 @@
         return data.tobytes()
 
 
+BaseDbType = TypeVar("BaseDbType", bound="BaseDb")
+
+
 class BaseDb:
     """Base class for swh.*.*Db.
 
@@ -119,8 +123,8 @@
 
     """
 
-    @classmethod
-    def adapt_conn(cls, conn):
+    @staticmethod
+    def adapt_conn(conn: psycopg2.extensions.connection):
         """Makes psycopg2 use 'bytes' to decode bytea instead of
         'memoryview', for this connection."""
         t_bytes = psycopg2.extensions.new_type((17,), "bytea", typecast_bytea)
@@ -130,7 +134,7 @@
         psycopg2.extensions.register_type(t_bytes_array, conn)
 
     @classmethod
-    def connect(cls, *args, **kwargs):
+    def connect(cls: Type[BaseDbType], *args, **kwargs) -> BaseDbType:
         """factory method to create a DB proxy
 
         Accepts all arguments of psycopg2.connect; only some specific
@@ -144,11 +148,17 @@
         return cls(conn)
 
     @classmethod
-    def from_pool(cls, pool):
+    def from_pool(
+        cls: Type[BaseDbType], pool: psycopg2.pool.AbstractConnectionPool
+    ) -> BaseDbType:
         conn = pool.getconn()
         return cls(conn, pool=pool)
 
-    def __init__(self, conn, pool=None):
+    def __init__(
+        self,
+        conn: psycopg2.extensions.connection,
+        pool: Optional[psycopg2.pool.AbstractConnectionPool] = None,
+    ):
         """create a DB proxy
 
         Args:
@@ -160,11 +170,13 @@
         self.conn = conn
         self.pool = pool
 
-    def put_conn(self):
+    def put_conn(self) -> None:
         if self.pool:
             self.pool.putconn(self.conn)
 
-    def cursor(self, cur_arg=None):
+    def cursor(
+        self, cur_arg: Optional[psycopg2.extensions.cursor] = None
+    ) -> psycopg2.extensions.cursor:
         """get a cursor: from cur_arg if given, or a fresh one otherwise
 
         meant to avoid boilerplate if/then/else in methods that proxy stored
@@ -179,7 +191,7 @@
     _cursor = cursor  # for bw compat
 
     @contextmanager
-    def transaction(self):
+    def transaction(self) -> Iterator[psycopg2.extensions.cursor]:
         """context manager to execute within a DB transaction
 
         Yields:
@@ -283,5 +295,5 @@
                 # postgresql returned an error, let's raise it.
                 raise exc_info[1].with_traceback(exc_info[2])
 
-    def mktemp(self, tblname, cur=None):
+    def mktemp(self, tblname: str, cur: Optional[psycopg2.extensions.cursor] = None):
         self.cursor(cur).execute("SELECT swh_mktemp(%s)", (tblname,))