diff --git a/swh/storage/proxies/retry.py b/swh/storage/proxies/retry.py
--- a/swh/storage/proxies/retry.py
+++ b/swh/storage/proxies/retry.py
@@ -6,8 +6,10 @@
 import logging
 import traceback
 
-from tenacity import retry, stop_after_attempt, wait_random_exponential
+from tenacity import RetryCallState, retry, stop_after_attempt, wait_random_exponential
+from tenacity.wait import wait_base
 
+from swh.core.api import TransientRemoteException
 from swh.storage import get_storage
 from swh.storage.exc import StorageArgumentException
 from swh.storage.interface import StorageInterface
@@ -15,9 +17,10 @@
 logger = logging.getLogger(__name__)
 
 
-def should_retry_adding(retry_state) -> bool:
+def should_retry_adding(retry_state: RetryCallState) -> bool:
     """Retry if the error/exception is (probably) not about a caller error"""
     attempt = retry_state.outcome
+    assert attempt
 
     if attempt.failed:
         error = attempt.exception()
@@ -48,9 +51,25 @@
         return False
 
 
+class wait_transient_exceptions(wait_base):
+    """Wait longer when servers return HTTP 503."""
+
+    def __init__(self, wait: float) -> None:
+        self.wait = wait
+
+    def __call__(self, retry_state: RetryCallState) -> float:
+        attempt = retry_state.outcome
+        assert attempt
+
+        if attempt.failed and isinstance(attempt.exception(), TransientRemoteException):
+            return self.wait
+        else:
+            return 0.0
+
+
 swh_retry = retry(
     retry=should_retry_adding,
-    wait=wait_random_exponential(multiplier=1, max=10),
+    wait=wait_random_exponential(multiplier=1, max=10) + wait_transient_exceptions(10),
     stop=stop_after_attempt(3),
     reraise=True,
 )
diff --git a/swh/storage/tests/test_retry.py b/swh/storage/tests/test_retry.py
--- a/swh/storage/tests/test_retry.py
+++ b/swh/storage/tests/test_retry.py
@@ -9,6 +9,7 @@
 import psycopg2
 import pytest
 
+from swh.core.api import TransientRemoteException
 from swh.storage.exc import HashCollision, StorageArgumentException
 from swh.storage.utils import now
 
@@ -77,6 +78,7 @@
 
     sample_content = sample_data.content
 
+    sleep = mocker.patch("time.sleep")
     content = swh_storage.content_get_data(sample_content.sha1)
     assert content is None
 
@@ -91,6 +93,52 @@
         ]
     )
 
+    assert len(sleep.mock_calls) == 2
+    (_name, args1, _kwargs) = sleep.mock_calls[0]
+    (_name, args2, _kwargs) = sleep.mock_calls[1]
+    assert 0 < args1[0] < 1
+    assert 0 < args2[0] < 2
+
+
+def test_retrying_proxy_storage_content_add_with_retry_of_transient(
+    monkeypatch_sleep,
+    swh_storage,
+    sample_data,
+    mocker,
+):
+    """Multiple retries for hash collision and psycopg2 error but finally ok
+    after many attempts"""
+    mock_memory = mocker.patch("swh.storage.in_memory.InMemoryStorage.content_add")
+    mock_memory.side_effect = [
+        TransientRemoteException("temporary failure"),
+        TransientRemoteException("temporary failure"),
+        # ok then!
+        {"content:add": 1},
+    ]
+
+    sample_content = sample_data.content
+
+    content = swh_storage.content_get_data(sample_content.sha1)
+    assert content is None
+
+    sleep = mocker.patch("time.sleep")
+    s = swh_storage.content_add([sample_content])
+    assert s == {"content:add": 1}
+
+    mock_memory.assert_has_calls(
+        [
+            call([sample_content]),
+            call([sample_content]),
+            call([sample_content]),
+        ]
+    )
+
+    assert len(sleep.mock_calls) == 2
+    (_name, args1, _kwargs) = sleep.mock_calls[0]
+    (_name, args2, _kwargs) = sleep.mock_calls[1]
+    assert 10 < args1[0] < 11
+    assert 10 < args2[0] < 12
+
 
 def test_retrying_proxy_swh_storage_content_add_failure(
     swh_storage, sample_data, mocker