zarr-developers · d-v-b · Jul 8, 2026 · May 31, 2026 · Jun 6, 2026 · Jun 6, 2026
diff --git a/changes/4133.doc.md b/changes/4133.doc.md
@@ -0,0 +1 @@
+Fixed the documented default of ``max_age_seconds`` in the ``CacheStore`` docstring: the default is ``"infinity"`` (no expiration), not ``None``, which is rejected. Also noted that ``cache_store`` must support deletes.
diff --git a/src/zarr/experimental/cache_store.py b/src/zarr/experimental/cache_store.py
@@ -52,10 +52,11 @@ class CacheStore(WrapperStore[Store]):
     store : Store
         The underlying store to wrap with caching
     cache_store : Store
-        The store to use for caching (can be any Store implementation)
-    max_age_seconds : int | None, optional
-        Maximum age of cached entries in seconds. None means no expiration.
-        Default is None.
+        The store to use for caching (can be any Store implementation that
+        supports deletes)
+    max_age_seconds : int or "infinity", optional
+        Maximum age of cached entries in seconds. The string "infinity" means
+        entries never expire. Default is "infinity".
     max_size : int | None, optional
         Maximum size of the cache in bytes. When exceeded, least recently used
         items are evicted. None means unlimited size. Default is None.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fixed the documented default of ``max_age_seconds`` in the ``CacheStore`` docstring: the default is ``"infinity"`` (no expiration), not ``None``, which is rejected. Also noted that ``cache_store`` must support deletes.