diff --git a/transfer_queue/config.yaml b/transfer_queue/config.yaml
index 4759c36..8a6df3d 100644
--- a/transfer_queue/config.yaml
+++ b/transfer_queue/config.yaml
@@ -23,8 +23,9 @@ backend:
 
   # SimpleStorage: ZMQ-based in-memory storage for out-of-the-box usage
   SimpleStorage:
-    # Maximum number of experience samples to hold across all storage units
-    total_storage_size: 100000
+    # Maximum number of experience samples to hold across all storage units.
+    # Set to null for unlimited capacity (no capacity check).
+    total_storage_size: null
     # Number of distributed storage units.
     # Recommended: >= 2 x number of nodes for load balancing.
     num_data_storage_units: 2
diff --git a/transfer_queue/storage/bootstrap/simple_storage_bootstrap.py b/transfer_queue/storage/bootstrap/simple_storage_bootstrap.py
index 1ab2f6b..adbd539 100644
--- a/transfer_queue/storage/bootstrap/simple_storage_bootstrap.py
+++ b/transfer_queue/storage/bootstrap/simple_storage_bootstrap.py
@@ -33,16 +33,21 @@ def initialize_simple_storage(conf: DictConfig) -> dict[str, Any]:
 
     simple_storage_handles = {}
     num_data_storage_units = conf.backend.SimpleStorage.num_data_storage_units
-    total_storage_size = conf.backend.SimpleStorage.total_storage_size
+    total_storage_size = conf.backend.SimpleStorage.get("total_storage_size", None)
     storage_placement_group = get_placement_group(num_data_storage_units, num_cpus_per_actor=1)
 
+    # Compute per-unit capacity: None means unlimited
+    storage_unit_size = (
+        math.ceil(total_storage_size / num_data_storage_units) if total_storage_size is not None else None
+    )
+
     for storage_unit_rank in range(num_data_storage_units):
         storage_node = SimpleStorageUnit.options(  # type: ignore[attr-defined]
             placement_group=storage_placement_group,
             placement_group_bundle_index=storage_unit_rank,
             name=f"TransferQueueStorageUnit#{storage_unit_rank}",
         ).remote(
-            storage_unit_size=math.ceil(total_storage_size / num_data_storage_units),
+            storage_unit_size=storage_unit_size,
         )
         simple_storage_handles[f"TransferQueueStorageUnit#{storage_unit_rank}"] = storage_node
         logger.info(f"TransferQueueStorageUnit#{storage_unit_rank} has been created.")
diff --git a/transfer_queue/storage/simple_storage.py b/transfer_queue/storage/simple_storage.py
index e70648e..6865a60 100644
--- a/transfer_queue/storage/simple_storage.py
+++ b/transfer_queue/storage/simple_storage.py
@@ -60,10 +60,10 @@ class StorageUnitData:
         }
     """
 
-    def __init__(self, storage_size: int):
+    def __init__(self, storage_size: int | None = None):
         # field_name -> {global_index: data} nested dict
         self.field_data: dict[str, dict] = {}
-        # Capacity upper bound (not pre-allocated list length)
+        # Capacity upper bound (None means unlimited)
         self.storage_size = storage_size
         # Track active global_index keys for O(1) capacity checks
         self._active_keys: set = set()
@@ -103,12 +103,13 @@ def put_data(self, field_data: dict[str, Any], global_indexes: list) -> None:
             global_indexes: Global indexes to use as dict keys.
         """
         # Capacity is enforced per unique sample key, not counted per-field
-        new_global_keys = [k for k in global_indexes if k not in self._active_keys]
-        if len(self._active_keys) + len(new_global_keys) > self.storage_size:
-            raise ValueError(
-                f"Storage capacity exceeded: {len(self._active_keys)} existing + "
-                f"{len(new_global_keys)} new > {self.storage_size}"
-            )
+        if self.storage_size is not None:
+            new_global_keys = [k for k in global_indexes if k not in self._active_keys]
+            if len(self._active_keys) + len(new_global_keys) > self.storage_size:
+                raise ValueError(
+                    f"Storage capacity exceeded: {len(self._active_keys)} existing + "
+                    f"{len(new_global_keys)} new > {self.storage_size}"
+                )
         for f, values in field_data.items():
             if len(values) != len(global_indexes):
                 raise ValueError(
@@ -152,11 +153,12 @@ class SimpleStorageUnit:
         zmq_server_info: ZMQ connection information for clients.
     """
 
-    def __init__(self, storage_unit_size: int):
+    def __init__(self, storage_unit_size: int | None = None):
         """Initialize a SimpleStorageUnit with the specified size.
 
         Args:
             storage_unit_size: Maximum number of elements that can be stored in this storage unit.
+                If None, the storage unit has unlimited capacity.
         """
         self.storage_unit_id = f"TQ_STORAGE_UNIT_{uuid4().hex[:8]}"
         self.storage_unit_size = storage_unit_size