diff --git a/swh/graphql/resolvers/base_connection.py b/swh/graphql/resolvers/base_connection.py
--- a/swh/graphql/resolvers/base_connection.py
+++ b/swh/graphql/resolvers/base_connection.py
@@ -8,6 +8,8 @@
 from dataclasses import dataclass
 from typing import Any, List, Optional, Type, Union
 
+from graphql.type import GraphQLResolveInfo
+
 from swh.graphql.backends.archive import Archive
 from swh.graphql.backends.search import Search
 from swh.graphql.errors import PaginationError
@@ -39,9 +41,10 @@
     _max_page_size: int = 1000  # maximum page size(max value for the first arg)
 
     def __init__(self, obj, info, paged_data=None, **kwargs):
-        self.obj: Optional[Any] = obj
-        self.info = info
+        self.obj: Optional[BaseNode] = obj
+        self.info: GraphQLResolveInfo = info
         self.kwargs = kwargs
+        # initialize commonly used vars
         self.archive = Archive()
         self.search = Search()
         self._paged_data: PagedResult = paged_data
@@ -109,7 +112,7 @@
         # FIXME, make this call async (not for v1)
         return None
 
-    def _get_after_arg(self) -> str:
+    def _get_after_arg(self):
         """
         Return the decoded next page token. Override to support a different
         cursor type
diff --git a/swh/graphql/resolvers/base_node.py b/swh/graphql/resolvers/base_node.py
--- a/swh/graphql/resolvers/base_node.py
+++ b/swh/graphql/resolvers/base_node.py
@@ -3,28 +3,32 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-from abc import ABC
 from collections import namedtuple
+from typing import Any, Optional, Union
 
+from graphql.type import GraphQLResolveInfo
+
+from swh.graphql import resolvers as rs
 from swh.graphql.backends.archive import Archive
 from swh.graphql.errors import ObjectNotFoundError
 
 
-class BaseNode(ABC):
+class BaseNode:
     """
     Base resolver for all the nodes
     """
 
-    def __init__(self, obj, info, node_data=None, **kwargs):
-        self.obj = obj
-        self.info = info
+    def __init__(self, obj, info, node_data: Optional[Any] = None, **kwargs):
+        self.obj: Optional[Union[BaseNode, rs.base_connection.BaseConnection]] = obj
+        self.info: GraphQLResolveInfo = info
         self.kwargs = kwargs
+        # initialize commonly used vars
         self.archive = Archive()
-        self._node = self._get_node(node_data)
+        self._node: Optional[Any] = self._get_node(node_data)
         # handle the errors, if any, after _node is set
         self._handle_node_errors()
 
-    def _get_node(self, node_data):
+    def _get_node(self, node_data: Optional[Any]) -> Optional[Any]:
         """
         Get the node object from the given data
         if the data (node_data) is none make a function call
@@ -34,7 +38,7 @@
             node_data = self._get_node_data()
         return self._get_node_from_data(node_data)
 
-    def _get_node_from_data(self, node_data):
+    def _get_node_from_data(self, node_data: Any) -> Optional[Any]:
         """
         Get the object from node_data
         In case of a dict, convert it to an object
@@ -44,7 +48,7 @@
             return namedtuple("NodeObj", node_data.keys())(*node_data.values())
         return node_data
 
-    def _handle_node_errors(self):
+    def _handle_node_errors(self) -> None:
         """
         Handle any error related to node data
 
@@ -54,7 +58,7 @@
         if self._node is None:
             raise ObjectNotFoundError("Requested object is not available")
 
-    def _get_node_data(self):
+    def _get_node_data(self) -> Optional[Any]:
         """
         Override for desired behaviour
         This will be called only when node_data is None
@@ -62,14 +66,14 @@
         # FIXME, make this call async (not for v1)
         return None
 
-    def __getattr__(self, name):
+    def __getattr__(self, name: str) -> Any:
         """
         Any property defined in the sub-class will get precedence over
         the _node attributes
         """
         return getattr(self._node, name)
 
-    def is_type_of(self):
+    def is_type_of(self) -> str:
         return self.__class__.__name__
 
 
diff --git a/swh/graphql/resolvers/resolver_factory.py b/swh/graphql/resolvers/resolver_factory.py
--- a/swh/graphql/resolvers/resolver_factory.py
+++ b/swh/graphql/resolvers/resolver_factory.py
@@ -26,7 +26,7 @@
 from .visit_status import LatestVisitStatusNode, VisitStatusConnection
 
 
-def get_node_resolver(resolver_type):
+def get_node_resolver(resolver_type: str):
     # FIXME, replace with a proper factory method
     mapping = {
         "origin": OriginNode,
@@ -68,7 +68,7 @@
     return mapping[resolver_type]
 
 
-def get_connection_resolver(resolver_type):
+def get_connection_resolver(resolver_type: str):
     # FIXME, replace with a proper factory method
     mapping = {
         "origins": OriginConnection,
diff --git a/swh/graphql/resolvers/resolvers.py b/swh/graphql/resolvers/resolvers.py
--- a/swh/graphql/resolvers/resolvers.py
+++ b/swh/graphql/resolvers/resolvers.py
@@ -16,7 +16,7 @@
 #   Every scalar is expected to resolve this way
 # - As an attribute/item in the object/dict returned by a backend (eg: Origin.url)
 
-from typing import Optional
+from typing import Optional, Union
 
 from ariadne import ObjectType, UnionType
 from graphql.type import GraphQLResolveInfo
@@ -57,7 +57,7 @@
 
 @origin.field("latestVisit")
 def latest_visit_resolver(
-    obj: rs.origin.OriginNode, info: GraphQLResolveInfo, **kw
+    obj: rs.origin.BaseOriginNode, info: GraphQLResolveInfo, **kw
 ) -> rs.visit.LatestVisitNode:
     """ """
     resolver = get_node_resolver("latest-visit")
@@ -75,7 +75,7 @@
 
 @visit.field("latestStatus")
 def latest_visit_status_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.visit.BaseVisitNode, info: GraphQLResolveInfo, **kw
 ) -> rs.visit_status.LatestVisitStatusNode:
     """ """
     resolver = get_node_resolver("latest-status")
@@ -104,7 +104,14 @@
 @snapshot_branch.field("target")
 def snapshot_branch_target_resolver(
     obj: rs.snapshot_branch.BaseSnapshotBranchNode, info: GraphQLResolveInfo, **kw
-):
+) -> Union[
+    rs.revision.BaseRevisionNode,
+    rs.release.BaseReleaseNode,
+    rs.directory.BaseDirectoryNode,
+    rs.content.BaseContentNode,
+    rs.snapshot.BaseSnapshotNode,
+    rs.snapshot_branch.BaseSnapshotBranchNode,
+]:
     """
     Snapshot branch target can be a revision, release, directory,
     content, snapshot or a branch itself (alias type)
@@ -124,7 +131,7 @@
 
 @revision.field("directory")
 def revision_directory_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.revision.BaseRevisionNode, info: GraphQLResolveInfo, **kw
 ) -> rs.directory.RevisionDirectoryNode:
     resolver = get_node_resolver("revision-directory")
     return resolver(obj, info, **kw)
@@ -139,7 +146,14 @@
 
 
 @release.field("target")
-def release_target_resolver(obj, info: GraphQLResolveInfo, **kw):
+def release_target_resolver(
+    obj: rs.release.BaseReleaseNode, info: GraphQLResolveInfo, **kw
+) -> Union[
+    rs.revision.BaseRevisionNode,
+    rs.release.BaseReleaseNode,
+    rs.directory.BaseDirectoryNode,
+    rs.content.BaseContentNode,
+]:
     """
     release target can be a release, revision,
     directory or content
@@ -162,7 +176,7 @@
 @query.field("directoryEntry")
 def directory_entry_resolver(
     obj: None, info: GraphQLResolveInfo, **kw
-) -> rs.directory.DirectoryNode:
+) -> rs.directory_entry.DirectoryEntryNode:
     resolver = get_node_resolver("directory-entry")
     return resolver(obj, info, **kw)
 
@@ -170,9 +184,13 @@
 @directory_entry.field("target")
 def directory_entry_target_resolver(
     obj: rs.directory_entry.BaseDirectoryEntryNode, info: GraphQLResolveInfo, **kw
-):
+) -> Union[
+    rs.revision.BaseRevisionNode,
+    rs.directory.BaseDirectoryNode,
+    rs.content.BaseContentNode,
+]:
     """
-    directory entry target can be a directory or a content
+    directory entry target can be a directory, content or a revision
     """
     resolver_type = f"dir-entry-{obj.type}"
     resolver = get_node_resolver(resolver_type)
@@ -190,7 +208,14 @@
 @search_result.field("target")
 def search_result_target_resolver(
     obj: rs.search.SearchResultNode, info: GraphQLResolveInfo, **kw
-):
+) -> Union[
+    rs.origin.BaseOriginNode,
+    rs.snapshot.BaseSnapshotNode,
+    rs.revision.BaseRevisionNode,
+    rs.release.BaseReleaseNode,
+    rs.directory.BaseDirectoryNode,
+    rs.content.BaseContentNode,
+]:
     resolver_type = f"search-result-{obj.type}"
     resolver = get_node_resolver(resolver_type)
     return resolver(obj, info, **kw)
@@ -218,7 +243,7 @@
 
 @origin.field("visits")
 def visits_resolver(
-    obj: rs.origin.OriginNode, info: GraphQLResolveInfo, **kw
+    obj: rs.origin.BaseOriginNode, info: GraphQLResolveInfo, **kw
 ) -> rs.visit.OriginVisitConnection:
     resolver = get_connection_resolver("origin-visits")
     return resolver(obj, info, **kw)
@@ -226,7 +251,7 @@
 
 @origin.field("snapshots")
 def origin_snapshots_resolver(
-    obj: rs.origin.OriginNode, info: GraphQLResolveInfo, **kw
+    obj: rs.origin.BaseOriginNode, info: GraphQLResolveInfo, **kw
 ) -> rs.snapshot.OriginSnapshotConnection:
     """ """
     resolver = get_connection_resolver("origin-snapshots")
@@ -235,7 +260,7 @@
 
 @visit.field("status")
 def visitstatus_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.visit.BaseVisitNode, info: GraphQLResolveInfo, **kw
 ) -> rs.visit_status.VisitStatusConnection:
     resolver = get_connection_resolver("visit-status")
     return resolver(obj, info, **kw)
@@ -243,7 +268,7 @@
 
 @snapshot.field("branches")
 def snapshot_branches_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.snapshot.BaseSnapshotNode, info: GraphQLResolveInfo, **kw
 ) -> rs.snapshot_branch.SnapshotBranchConnection:
     resolver = get_connection_resolver("snapshot-branches")
     return resolver(obj, info, **kw)
@@ -251,21 +276,23 @@
 
 @revision.field("parents")
 def revision_parents_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.revision.BaseRevisionNode, info: GraphQLResolveInfo, **kw
 ) -> rs.revision.ParentRevisionConnection:
     resolver = get_connection_resolver("revision-parents")
     return resolver(obj, info, **kw)
 
 
 @revision.field("revisionLog")
-def revision_log_resolver(obj, info, **kw):
+def revision_log_resolver(
+    obj: rs.revision.BaseRevisionNode, info: GraphQLResolveInfo, **kw
+) -> rs.revision.LogRevisionConnection:
     resolver = get_connection_resolver("revision-log")
     return resolver(obj, info, **kw)
 
 
 @directory.field("entries")
 def directory_entries_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: rs.directory.BaseDirectoryNode, info: GraphQLResolveInfo, **kw
 ) -> rs.directory_entry.DirectoryEntryConnection:
     resolver = get_connection_resolver("directory-entries")
     return resolver(obj, info, **kw)
@@ -273,7 +300,7 @@
 
 @query.field("resolveSwhid")
 def search_swhid_resolver(
-    obj, info: GraphQLResolveInfo, **kw
+    obj: None, info: GraphQLResolveInfo, **kw
 ) -> rs.search.ResolveSwhidConnection:
     resolver = get_connection_resolver("resolve-swhid")
     return resolver(obj, info, **kw)
@@ -281,8 +308,8 @@
 
 @query.field("search")
 def search_resolver(
-    obj, info: GraphQLResolveInfo, **kw
-) -> rs.search.ResolveSwhidConnection:
+    obj: None, info: GraphQLResolveInfo, **kw
+) -> rs.search.SearchConnection:
     resolver = get_connection_resolver("search")
     return resolver(obj, info, **kw)
 
@@ -294,7 +321,18 @@
 @directory_entry_target.type_resolver
 @branch_target.type_resolver
 @search_result_target.type_resolver
-def union_resolver(obj, *_) -> str:
+def union_resolver(
+    obj: Union[
+        rs.origin.BaseOriginNode,
+        rs.revision.BaseRevisionNode,
+        rs.release.BaseReleaseNode,
+        rs.directory.BaseDirectoryNode,
+        rs.content.BaseContentNode,
+        rs.snapshot.BaseSnapshotNode,
+        rs.snapshot_branch.BaseSnapshotBranchNode,
+    ],
+    *_,
+) -> str:
     """
     Generic resolver for all the union types
     """
@@ -302,10 +340,10 @@
 
 
 @binary_string.field("text")
-def binary_string_text_resolver(obj, *args, **kw):
+def binary_string_text_resolver(obj: bytes, *args, **kw) -> str:
     return obj.decode(utils.ENCODING, "replace")
 
 
 @binary_string.field("base64")
-def binary_string_base64_resolver(obj, *args, **kw):
+def binary_string_base64_resolver(obj: bytes, *args, **kw) -> str:
     return utils.get_b64_string(obj)
diff --git a/swh/graphql/utils/utils.py b/swh/graphql/utils/utils.py
--- a/swh/graphql/utils/utils.py
+++ b/swh/graphql/utils/utils.py
@@ -24,7 +24,7 @@
     return get_b64_string(cursor)
 
 
-def get_decoded_cursor(cursor: str) -> str:
+def get_decoded_cursor(cursor: Optional[str]) -> Optional[str]:
     if cursor is None:
         return None
     return base64.b64decode(cursor, validate=True).decode()