diff --git a/swh/loader/package/cran/loader.py b/swh/loader/package/cran/loader.py
--- a/swh/loader/package/cran/loader.py
+++ b/swh/loader/package/cran/loader.py
@@ -196,7 +196,7 @@
             # received datetime without timezone: 2001-06-08 00:00:00
             dt = dt.replace(tzinfo=timezone.utc)
     except Exception as e:
-        logger.warning("Fail to parse date %s. Reason: %s", (date, e))
+        logger.warning("Fail to parse date %s. Reason: %s", date, e)
     if dt:
         return TimestampWithTimezone.from_datetime(dt)
     else:
diff --git a/swh/loader/package/deposit/loader.py b/swh/loader/package/deposit/loader.py
--- a/swh/loader/package/deposit/loader.py
+++ b/swh/loader/package/deposit/loader.py
@@ -28,7 +28,7 @@
     PackageLoader,
     RawExtrinsicMetadataCore,
 )
-from swh.loader.package.utils import download
+from swh.loader.package.utils import cached_method, download
 
 
 logger = logging.getLogger(__name__)
@@ -86,7 +86,6 @@
                 RawExtrinsicMetadataCore(
                     format="sword-v2-atom-codemeta-v2-in-json",
                     metadata=raw_metadata_from_origin,
-                    discovery_date=None,
                 ),
             ],
         )
@@ -112,7 +111,6 @@
         config_deposit = self.config["deposit"]
         self.deposit_id = deposit_id
         self.client = ApiClient(url=config_deposit["url"], auth=config_deposit["auth"])
-        self.metadata: Dict[str, Any] = {}
 
     def get_versions(self) -> Sequence[str]:
         # only 1 branch 'HEAD' with no alias since we only have 1 snapshot
@@ -120,7 +118,7 @@
         return ["HEAD"]
 
     def get_metadata_authority(self) -> MetadataAuthority:
-        provider = self.metadata["origin_metadata"]["provider"]
+        provider = self.metadata()["origin_metadata"]["provider"]
         assert provider["provider_type"] == "deposit_client"
         return MetadataAuthority(
             type=MetadataAuthorityType.DEPOSIT_CLIENT,
@@ -132,7 +130,7 @@
         )
 
     def get_metadata_fetcher(self) -> MetadataFetcher:
-        tool = self.metadata["origin_metadata"]["tool"]
+        tool = self.metadata()["origin_metadata"]["tool"]
         return MetadataFetcher(
             name=tool["name"], version=tool["version"], metadata=tool["configuration"],
         )
@@ -141,7 +139,7 @@
         self, version: str
     ) -> Iterator[Tuple[str, DepositPackageInfo]]:
         p_info = DepositPackageInfo.from_metadata(
-            self.metadata, url=self.url, filename="archive.zip",
+            self.metadata(), url=self.url, filename="archive.zip",
         )
         yield "HEAD", p_info
 
@@ -180,19 +178,23 @@
         )
 
     def get_extrinsic_origin_metadata(self) -> List[RawExtrinsicMetadataCore]:
-        origin_metadata = self.metadata["origin_metadata"]
+        origin_metadata = self.metadata()["origin_metadata"]
         return [
             RawExtrinsicMetadataCore(
                 format="sword-v2-atom-codemeta-v2-in-json",
                 metadata=json.dumps(origin_metadata["metadata"]).encode(),
-                discovery_date=None,
             )
         ]
 
+    @cached_method
+    def metadata(self):
+        """Returns metadata from the deposit server"""
+        return self.client.metadata_get(self.deposit_id)
+
     def load(self) -> Dict:
         # First making sure the deposit is known prior to trigger a loading
         try:
-            self.metadata = self.client.metadata_get(self.deposit_id)
+            self.metadata()
         except ValueError:
             logger.error(f"Unknown deposit {self.deposit_id}, ignoring")
             return {"status": "failed"}
diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -64,7 +64,7 @@
 
     format = attr.ib(type=str)
     metadata = attr.ib(type=bytes)
-    discovery_date = attr.ib(type=Optional[datetime.datetime])
+    discovery_date = attr.ib(type=Optional[datetime.datetime], default=None)
     """Defaults to the visit date."""
 
 
diff --git a/swh/loader/package/nixguix/loader.py b/swh/loader/package/nixguix/loader.py
--- a/swh/loader/package/nixguix/loader.py
+++ b/swh/loader/package/nixguix/loader.py
@@ -89,9 +89,7 @@
     def get_extrinsic_snapshot_metadata(self):
         return [
             RawExtrinsicMetadataCore(
-                format="nixguix-sources-json",
-                metadata=self.raw_sources,
-                discovery_date=None,
+                format="nixguix-sources-json", metadata=self.raw_sources,
             ),
         ]
 
diff --git a/swh/loader/package/npm/loader.py b/swh/loader/package/npm/loader.py
--- a/swh/loader/package/npm/loader.py
+++ b/swh/loader/package/npm/loader.py
@@ -15,6 +15,8 @@
 
 from urllib.parse import quote
 from swh.model.model import (
+    MetadataAuthority,
+    MetadataAuthorityType,
     Person,
     RevisionType,
     Revision,
@@ -22,8 +24,12 @@
     Sha1Git,
 )
 
-from swh.loader.package.loader import BasePackageInfo, PackageLoader
-from swh.loader.package.utils import api_info, release_name
+from swh.loader.package.loader import (
+    BasePackageInfo,
+    PackageLoader,
+    RawExtrinsicMetadataCore,
+)
+from swh.loader.package.utils import api_info, cached_method, release_name
 
 
 logger = logging.getLogger(__name__)
@@ -90,24 +96,38 @@
         self._info: Dict[str, Any] = {}
         self._versions = None
 
-    @property
-    def info(self) -> Dict[str, Any]:
+    @cached_method
+    def _raw_info(self) -> bytes:
+        return api_info(self.provider_url)
+
+    @cached_method
+    def info(self) -> Dict:
         """Return the project metadata information (fetched from npm registry)
 
         """
-        if not self._info:
-            self._info = json.loads(api_info(self.provider_url))
-        return self._info
+        return json.loads(self._raw_info())
 
     def get_versions(self) -> Sequence[str]:
-        return sorted(list(self.info["versions"].keys()))
+        return sorted(list(self.info()["versions"].keys()))
 
     def get_default_version(self) -> str:
-        return self.info["dist-tags"].get("latest", "")
+        return self.info()["dist-tags"].get("latest", "")
+
+    def get_metadata_authority(self):
+        return MetadataAuthority(
+            type=MetadataAuthorityType.FORGE, url="https://npmjs.com/", metadata={},
+        )
+
+    def get_extrinsic_snapshot_metadata(self):
+        return [
+            RawExtrinsicMetadataCore(
+                format="replicate-npm-package-json", metadata=self._raw_info(),
+            ),
+        ]
 
     def get_package_info(self, version: str) -> Iterator[Tuple[str, NpmPackageInfo]]:
         p_info = NpmPackageInfo.from_metadata(
-            project_metadata=self.info, version=version
+            project_metadata=self.info(), version=version
         )
         yield release_name(version), p_info
 
diff --git a/swh/loader/package/npm/tests/test_npm.py b/swh/loader/package/npm/tests/test_npm.py
--- a/swh/loader/package/npm/tests/test_npm.py
+++ b/swh/loader/package/npm/tests/test_npm.py
@@ -7,9 +7,23 @@
 import os
 import pytest
 
-from swh.model.hashutil import hash_to_bytes
-from swh.model.model import Person, Snapshot, SnapshotBranch, TargetType
+from swh.model.hashutil import hash_to_bytes, hash_to_hex
+from swh.model.identifiers import SWHID
+from swh.model.model import (
+    MetadataAuthority,
+    MetadataAuthorityType,
+    MetadataFetcher,
+    MetadataTargetType,
+    Person,
+    RawExtrinsicMetadata,
+    Snapshot,
+    SnapshotBranch,
+    TargetType,
+)
+
+from swh.storage.interface import PagedResult
 
+from swh.loader.package import __version__
 from swh.loader.package.npm.loader import (
     _author_str,
     NpmLoader,
@@ -24,6 +38,12 @@
 )
 
 
+@pytest.fixture
+def org_api_info(datadir) -> bytes:
+    with open(os.path.join(datadir, "https_replicate.npmjs.com", "org"), "rb",) as f:
+        return f.read()
+
+
 def test_npm_author_str():
     for author, expected_author in [
         ("author", "author"),
@@ -322,7 +342,7 @@
         )
 
 
-def test_npm_loader_first_visit(swh_config, requests_mock_datadir):
+def test_npm_loader_first_visit(swh_config, requests_mock_datadir, org_api_info):
     package = "org"
     url = package_url(package)
     loader = NpmLoader(url)
@@ -387,6 +407,32 @@
     )
     check_snapshot(expected_snapshot, loader.storage)
 
+    snapshot_swhid = SWHID(
+        object_type="snapshot", object_id=hash_to_hex(expected_snapshot_id)
+    )
+    metadata_authority = MetadataAuthority(
+        type=MetadataAuthorityType.FORGE, url="https://npmjs.com/",
+    )
+    expected_metadata = [
+        RawExtrinsicMetadata(
+            type=MetadataTargetType.SNAPSHOT,
+            id=snapshot_swhid,
+            authority=metadata_authority,
+            fetcher=MetadataFetcher(
+                name="swh.loader.package.npm.loader.NpmLoader", version=__version__,
+            ),
+            discovery_date=loader.visit_date,
+            format="replicate-npm-package-json",
+            metadata=org_api_info,
+            origin="https://www.npmjs.com/package/org",
+        )
+    ]
+    assert loader.storage.raw_extrinsic_metadata_get(
+        type=MetadataTargetType.SNAPSHOT,
+        id=snapshot_swhid,
+        authority=metadata_authority,
+    ) == PagedResult(next_page_token=None, results=expected_metadata,)
+
 
 def test_npm_loader_incremental_visit(swh_config, requests_mock_datadir_visits):
     package = "org"
@@ -417,7 +463,10 @@
         "snapshot": 1,
     } == stats
 
-    loader._info = None  # reset loader internal state
+    # reset loader internal state
+    del loader._cached_info
+    del loader._cached__raw_info
+
     actual_load_status2 = loader.load()
     assert actual_load_status2["status"] == "eventful"
     snap_id2 = actual_load_status2["snapshot_id"]
diff --git a/swh/loader/package/pypi/loader.py b/swh/loader/package/pypi/loader.py
--- a/swh/loader/package/pypi/loader.py
+++ b/swh/loader/package/pypi/loader.py
@@ -13,6 +13,8 @@
 from pkginfo import UnpackedSDist
 
 from swh.model.model import (
+    MetadataAuthority,
+    MetadataAuthorityType,
     Person,
     Sha1Git,
     TimestampWithTimezone,
@@ -20,8 +22,17 @@
     RevisionType,
 )
 
-from swh.loader.package.loader import BasePackageInfo, PackageLoader
-from swh.loader.package.utils import api_info, release_name, EMPTY_AUTHOR
+from swh.loader.package.loader import (
+    BasePackageInfo,
+    PackageLoader,
+    RawExtrinsicMetadataCore,
+)
+from swh.loader.package.utils import (
+    api_info,
+    cached_method,
+    release_name,
+    EMPTY_AUTHOR,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -55,27 +66,43 @@
 
     def __init__(self, url):
         super().__init__(url=url)
-        self._info = None
         self.provider_url = pypi_api_url(self.url)
 
-    @property
+    @cached_method
+    def _raw_info(self) -> bytes:
+        return api_info(self.provider_url)
+
+    @cached_method
     def info(self) -> Dict:
         """Return the project metadata information (fetched from pypi registry)
 
         """
-        if not self._info:
-            self._info = json.loads(api_info(self.provider_url))
-        return self._info
+        return json.loads(self._raw_info())
 
     def get_versions(self) -> Sequence[str]:
-        return self.info["releases"].keys()
+        return self.info()["releases"].keys()
 
     def get_default_version(self) -> str:
-        return self.info["info"]["version"]
+        return self.info()["info"]["version"]
+
+    def get_metadata_authority(self):
+        p_url = urlparse(self.url)
+        return MetadataAuthority(
+            type=MetadataAuthorityType.FORGE,
+            url=f"{p_url.scheme}://{p_url.netloc}/",
+            metadata={},
+        )
+
+    def get_extrinsic_snapshot_metadata(self):
+        return [
+            RawExtrinsicMetadataCore(
+                format="pypi-project-json", metadata=self._raw_info(),
+            ),
+        ]
 
     def get_package_info(self, version: str) -> Iterator[Tuple[str, PyPIPackageInfo]]:
         res = []
-        for meta in self.info["releases"][version]:
+        for meta in self.info()["releases"][version]:
             if meta["packagetype"] != "sdist":
                 continue
             p_info = PyPIPackageInfo.from_metadata(meta)
diff --git a/swh/loader/package/pypi/tests/test_pypi.py b/swh/loader/package/pypi/tests/test_pypi.py
--- a/swh/loader/package/pypi/tests/test_pypi.py
+++ b/swh/loader/package/pypi/tests/test_pypi.py
@@ -13,9 +13,22 @@
 
 from swh.core.tarball import uncompress
 from swh.core.pytest_plugin import requests_mock_datadir_factory
-from swh.model.hashutil import hash_to_bytes
-from swh.model.model import Person, Snapshot, SnapshotBranch, TargetType
+from swh.model.hashutil import hash_to_bytes, hash_to_hex
+from swh.model.identifiers import SWHID
+from swh.model.model import (
+    MetadataAuthority,
+    MetadataAuthorityType,
+    MetadataFetcher,
+    MetadataTargetType,
+    Person,
+    RawExtrinsicMetadata,
+    Snapshot,
+    SnapshotBranch,
+    TargetType,
+)
+from swh.storage.interface import PagedResult
 
+from swh.loader.package import __version__
 from swh.loader.package.pypi.loader import (
     PyPILoader,
     pypi_api_url,
@@ -31,6 +44,14 @@
 )
 
 
+@pytest.fixture
+def _0805nexter_api_info(datadir) -> bytes:
+    with open(
+        os.path.join(datadir, "https_pypi.org", "pypi_0805nexter_json"), "rb",
+    ) as f:
+        return f.read()
+
+
 def test_author_basic():
     data = {
         "author": "i-am-groot",
@@ -315,6 +336,41 @@
         )
 
 
+def test_snapshot_metadata(swh_config, requests_mock_datadir, _0805nexter_api_info):
+    url = "https://pypi.org/project/0805nexter"
+    loader = PyPILoader(url)
+
+    actual_load_status = loader.load()
+    assert actual_load_status["status"] == "eventful"
+    assert actual_load_status["snapshot_id"] is not None
+
+    snapshot_swhid = SWHID(
+        object_type="snapshot", object_id=hash_to_hex(actual_load_status["snapshot_id"])
+    )
+    metadata_authority = MetadataAuthority(
+        type=MetadataAuthorityType.FORGE, url="https://pypi.org/",
+    )
+    expected_metadata = [
+        RawExtrinsicMetadata(
+            type=MetadataTargetType.SNAPSHOT,
+            id=snapshot_swhid,
+            authority=metadata_authority,
+            fetcher=MetadataFetcher(
+                name="swh.loader.package.pypi.loader.PyPILoader", version=__version__,
+            ),
+            discovery_date=loader.visit_date,
+            format="pypi-project-json",
+            metadata=_0805nexter_api_info,
+            origin=url,
+        )
+    ]
+    assert loader.storage.raw_extrinsic_metadata_get(
+        type=MetadataTargetType.SNAPSHOT,
+        id=snapshot_swhid,
+        authority=metadata_authority,
+    ) == PagedResult(next_page_token=None, results=expected_metadata,)
+
+
 def test_visit_with_missing_artifact(swh_config, requests_mock_datadir_missing_one):
     """Load a pypi project with some missing artifacts ends up with 1 snapshot
 
@@ -582,12 +638,13 @@
     } == visit1_stats
 
     # Reset internal state
-    loader._info = None
+    del loader._cached__raw_info
+    del loader._cached_info
 
     visit2_actual_load_status = loader.load()
     visit2_stats = get_stats(loader.storage)
 
-    assert visit2_actual_load_status["status"] == "eventful"
+    assert visit2_actual_load_status["status"] == "eventful", visit2_actual_load_status
     expected_snapshot_id2 = hash_to_bytes("2e5149a7b0725d18231a37b342e9b7c4e121f283")
     assert visit2_actual_load_status == {
         "status": "eventful",
diff --git a/swh/loader/package/utils.py b/swh/loader/package/utils.py
--- a/swh/loader/package/utils.py
+++ b/swh/loader/package/utils.py
@@ -4,11 +4,12 @@
 # See top-level LICENSE file for more information
 
 import copy
+import functools
 import logging
 import os
 import requests
 
-from typing import Dict, Optional, Tuple
+from typing import Callable, Dict, Optional, Tuple, TypeVar
 
 from swh.model.hashutil import MultiHash, HASH_BLOCK_SIZE
 from swh.model.model import Person
@@ -121,3 +122,23 @@
     if filename:
         return "releases/%s/%s" % (version, filename)
     return "releases/%s" % version
+
+
+TReturn = TypeVar("TReturn")
+TSelf = TypeVar("TSelf")
+
+_UNDEFINED = object()
+
+
+def cached_method(f: Callable[[TSelf], TReturn]) -> Callable[[TSelf], TReturn]:
+    cache_name = f"_cached_{f.__name__}"
+
+    @functools.wraps(f)
+    def newf(self):
+        value = getattr(self, cache_name, _UNDEFINED)
+        if value is _UNDEFINED:
+            value = f(self)
+            setattr(self, cache_name, value)
+        return value
+
+    return newf